Supporting fast fashion.
"Before turning 30 I made a decision to stop buying items that support fast fashion," Laura, an operations officer from London, told Business Insider. "That means no Zara! I have already given up on H&M and Primark. They say that most items are worn just seven times, so my goal is to buy things you will wear many times even if it costs more."
Clinging on to friendships that have run their course.
The further into your 20s you go, you may find the fewer friends you have. As you leave university and begin your career, some relationships just don't last the distance — and operations officer Laura says you should accept this.
"Having lived abroad for a number of years since uni, I learnt a while ago not to lose sleep over friendships that fall by the wayside. Now I put a lot more effort and time into worthwhile friendships.
Drinking cheap wine.
James, former technology editor at BI UK, said: "Drinking cheap wine is a damaging habit that I thankfully broke in recent years."
There's a theory that spending a few more pounds on a bottle might mean you savour it, enjoy it more, and possibly even drink less of it. Whether or not that's true, it's worth educating yourself on what you like.
Letting other people shop for you.
"By now you should have developed your own sense of style and figured out what clothes best represent who you are," said Tom, lifestyle reporter at BI UK. "By all means seek advice from fashionable friends but letting your mum or your girlfriend or anyone else shop for you will mask your personality in what you're wearing.
"Experiment, go shopping by yourself and eventually you will refine a style that you're comfortable in and that everyone else will recognize as iconically you."
Putting your physical health before your mental health.
"Don't put your (outwardly) physical health before your mental health," Megan, office manager and HR coordinator at BI UK, said. "Diet and exercise should make you feel good about yourself, not guilty. Routines are great but when the way you physically treat yourself affects the way you mentally treat yourself then the balance is wrong."
Not being able to cook for yourself.
Microwave meals and pot noodles are all very well when you're a student, but as you get a bit older, it starts to look a bit sad. According to Kieran, BI UK's news editor, knowing how to cook proper meals is a habit you have to get into.
Spending time with people who make you feel insignificant.
Megan said: "Cut the people who make you feel insignificant. Why pour energy into the people who don't like you when you could be spending time with the friends who love you?
"Not everyone is going to like you, so don't spend time forcing it. Learn to love the people who like you just as you are."
Running out of money at the end of the month.
"It's time to look at where your money goes, and look at ways of saving money without going without," Hannah, a charity worker from London, said.
There are plenty of budgeting apps out there that can help you to work out where you're spending most.
Not spending enough time with your parents.
"It can be easy to become 'too busy' to make plans with family a priority," said Ali, senior editor at BI UK. "However, as you get older, you realize how this is actually the most important thing. This can be as simple as picking up the phone a couple of times a week, going for lunch, or spending a weekend together as often as you can. Friends come and go, but your family will — and should — always be number one."
Never calling your older relatives.
If you have a lot of relatives, it can be easy to assume they will always be around. But this simply isn't true, and you'll kick yourself when they're gone that you didn't call them more.
"Pick up the phone and call your grandma," said Lindsay, psychology and relationships reporter at BI UK. "It won't take a long time out of your day, and it will mean so much to her. You don't want to wish you talked to her more when she's gone."
Comparing your life to other people's.
It's hard, but try to stop "looking sideways," said Leon, senior video producer at BI UK.
"Scrolling through Instagram and Facebook and comparing your life to the lives of your friends is not healthy," he said. "No one's Instagram life is real, people only post what they want other people to see, you need to be very aware of this while using these apps otherwise you'll constantly be thinking your life sucks and everyone else is having a great time and that simply isn't true."
Being a couch potato.
Sometimes it's necessary to have some "me time." But you'll feel a lot more accomplished if you actually get out and about some weekends. Claudia, a video producer at BI UK, said leaving the house is something you should definitely learn to do.
"Be active, have a hobby, take a day trip on Sundays or weekend in general rather than sitting on the couch all day," she said
As we get older, drama can feel more and more irritating. So don't hold grudges, said Rosie P, former lifestyle writer at BI UK.
"That unhealthy behavior is really damaging to past, present, and future relationships — you don't want to end up bitter," she said. "It's better to swallow pride and be the bigger person in the long run."
Spending more time watching TV than you do reading.
"Stop spending all of your time in front of the TV screen and never actually reading a book," said Ali. "You never feel good about yourself after a Netflix binge, but reading a book is both relaxing and educational. Whether it's a novel or non-fiction, it doesn't matter — it'll give you a sense of accomplishment that crushing episodes of a new series never will."
Not looking after your teeth.
That includes brushing twice a day, (even after nights out), regular visits to the dentist, and yes, flossing.
"You only have one set of teeth — so look after them!" Dina, managing editor at BI UK, said.
Obsessing over online dating.
You might be at the age where everyone else seems to be settling down, while you're still single, but you shouldn't obsessively worry about it. Definitely don't go on dates every night of the week out of desperation.
"If someone isn't right for you, they simply aren't right for you," said Lindsay. "Don't fret if someone you're dating hasn't replied to you in a few days, or people on dating apps aren't arranging anything with you. If they were the one, it would be easy, and they would be treating you properly. So stop trying to force it and let it happen organically."
Not wearing sunscreen.
"Over doing the sun bathing — as you get older it's even more important to look after and protect your skin," said Hannah.
And this isn't only while you're on the beach — most skin specialists recommend you introduce a moderate SPF factor into your daily skincare regime through winter as well as summer.
Constantly worrying about what people think.
Worrying about what people think was the single most popular habit to break of all of the colleagues and friends we spoke to, so it's probably worth taking note of.
Emily, a private chef from London, says: "I spent far too much of my 20s worrying about what other people think, generally worrying in my 20s was a real waste of energy."
Not having a long-term plan.
"Not having a long term plan is something that I have been guilty of," Leon said. "By the time you're 30 you should know what you want from life and have a rough idea of when you'll be moving/getting married/having children/changing jobs, etc."
Charlotte, an account manager in music, told Business Insider that in the leadup to her 30s she has started each year by sitting down and thinking through the main aspects of her life, from relationships to careers, to figure out what she wants to change or develop in each area.
Trying to store all important dates and appointments in your head.
Alan, sports reporter at BI UK, said: "Get a calendar and put all the important dates in it at the start of the year so you remember things."
Whether your system is paper or electronic, finding a system that works for you will make you feel more organised, which can help to reduce stress.