Love yourself.
No, I don't only mean to treat yourself with the most expensive clothes, take baths every single day, or take yourself on dates. There's much more to self love than these material stuff.
Love your soul and body wholeheartedly. You ought to look at yourself in the mirror, stare at every pimple at your face, trace your facial shape and every detail in it with your eyes, and scream love at it. Feel who you are deep down in your soul. All your flaws, imperfections, shortcomings, and your PAST. Forgive yourself. Tell yourself this is who you are, the person you have to live with your entire life. So if you're not gonna be the one looking at yourself that way, who will?
When you wake up in the morning, appreciate your messy hair, and your exhausted eyes. When you take a shower, take a look at how God perfectly shaped your body and be grateful for every ounce of it because yes, we are all perfect in our own way.
And what I mean by loving yourself, is to set limits for that beautiful self. Set limits as to who gets to be in your space. Who you allow to deal with. If you don't like someone, fine! Cut them off. Unapologetically.
NEVER accept to be treated as a second option. Walk away from people who threaten your piece of mind and add nothing of value or meaning to your little world.
That's what I mean by LOVE YOURSELF. Because if you don't, then who will?