In your 20s, there is a certain idealism of how you think your life will go. How put together you'll be by the time your 30. Maybe you have a rough timeline of when you'll have kids and work backwards to when you should meet the love of your life by. Maybe you have an idea of what title you should don or how much money you need to be making.
In your 20s, you'll beat yourself up. A lot. You are and will be your harshest critic. You'd never say the things you do to a friend, so why do we do it?
When you approach your 30s, as I will in a mere few minutes, there is (or at least I've worked on it enough for it to come to this point) a sense of peace. A certain acceptance that you have done what you could have with the situation you were given. You know better now. And with that, know you will do better.
In your almost 30s, when you see that life hasn't gone exactly as you've planned, as the young Meghan Trainor once said, you need to let it go.
If I were to give any advice, it'd be to get to know yourself, get comfortable and live your truth. Still, we're always a WIP.