Be Selective.

You don't have to be friends with everyone. ZakLorinator

Also don't be afraid to do what it takes to extract yourself from the situation if "being nice" only puts you in a dangerous position with somebody else. commandrix

Pen to Paper.

Write stuff down. Meetings, social engagements, doctor's appointments, shopping lists, tasks, errands you need to run tomorrow, bucket list ideas, that thing you wanna to tell your grandpa but it's midnight so you can't call him right now. All of it. aerdnadw

Wish I started this when young... it's amazing how many things you forget, including some great ideas you might come up with and other important things. Keeping up with all the details mentally in the world today is simply impossible once you're engulfed in the day to day grind. bizzybeerslugger

You're Special!

Don't put yourself down or spend time with those who do it for you. In other words was do not make yourself feel bad or allow others to make you feel bad about yourself. You could say that there are enough people in the world who will try and make you feel bad without you doing it to yourself as well. "Friends" that do this to you are absolutely not your friend. GOTO_GOSUB

Own It.

Confidence isn't "I know they'll like me." Confidence is "I'll be ok whether they like me or not." autistic_developer

"the juice ain't worth the squeeze."

Sometimes "the juice ain't worth the squeeze." All battles can be bitter, and the sweet taste of victory isn't always a great chaser. So pick your battles wisely.

edit: The focus is actually about taking on a lot of work and not seeing good returns for what you put in. Like working your hardest to squeeze an orange, but you don't get a lot of juice or it tastes weird. The juice isn't worth the squeeze. You can apply it to arguing if you like, but the focus is on an effort you are putting in. cerberus6320

Shhhhh.....

You don't always have to voice your opinion on everything. Sometimes it's just better to stay quiet. PM_garden_pics

I had a week off from Reddit/social media a while ago and once it was over I found myself thinking "this comment isn't necessary" and deleting it roughly half the time. It really made me realize how much of commenting on the internet is about wanting to be involved, rather than actually contributing something new to the discussion. HeroIsAGirlsName

The Receipts. 

Being able to buy something is not the same as being able to afford it. WatchTheBoom

As a note, this isn't just about credit. For some things (cars in particular) the ongoing upkeep costs can be more expensive than the purchase price over the long run.

Pets are another great example. Getting a pet is cheap, owning a pet is expensive. adeon

It's not about you....

People, largely, don't really care about you. Don't spend your whole life worrying what some stranger on the street is going to think about you, because chances are they won't; they'll be too busy worrying about what strangers are thinking of them.

Also, "There is nothing noble in being superior to your fellow men. True nobility lies in being superior to your former self." -Ernest Hemingway pm_me_n0Od

 "I have cancer!"

Having a serious disease or disability does not automatically make someone a good person. Naweezy

Yeah I remember a customer at my old job who had cancer and she was the meanest person I have ever dealt with and she always pulled the "I have cancer!" Card if she didn't get what she wanted. Candy26262

It's not Personal.

Try not to take things personally, 99% of the time when someone brings you negativity or criticism they are just talking to themselves or acting out their own conflict on others. If you can hold your peace in these times, other peoples problems with you will tell you a lot more about them, than you could learn about yourself from them. madeamashup