People in general ain't shyt. They're trash, they will step on you to win and generally have no real boundaries and so on when it comes to what they want. As another poster touched on, they're selfish. Whether in personal, professional or romantic relationships ... it doesn't matter. In general, people are flat out trash. Not all of them, but in general. No better than any of us.
I say that to say that if anything, people are gonna people. The sooner you understand that, the better off you will be. Control what you can control and the rest handles itself.
Learn who you are and what you're about as soon and as extensively as you can. Stand on that when it comes to big decisions.
In matters of dating/the heart, don't expect anyone to love you if you can't love yourself. That shyt permeates you.
Try to surround yourself with friends/people that can offer you a different perspective on things. People you can learn from, but most importantly, people who rock with you for being yourself.
Don't give a fukk about societal standards/norms, especially for people who are concerned about lagging behind in life or not doing what you felt you would have done by a certain age. Trust that God/fate/you wouldn't put yourself in a situation that you're not ready to handle/couldn't benefit from at that time. And yes, it's possible to learn from falling on your face.