Although you think you may have realized a little late, it definitely beats the hell of out living your entire life before this epiphany hits you on your death bed. I'm no saint, but I am dedicating more of my efforts towards my own future, and the happiness there for me.
I used to go with the flow as well, and got hurt a lot because of it. It's never an act of selfishness, but one of self-love to care for our own happiness. I hope that you had an excellent bday c: 💞