Read the title one more time. I know. It's easier said than done, but I'm serious.
One boy may break your trust. He may cheat on you. He may lie to you, deceive you, lust for you (not love you), twist the way you see yourself, completely ghost you, talk down to you, call you names, hurt you emotionally, verbally, and maybe even physically (though I hope it doesn't get to that point).
All of those things break apart a person, and demand of you to put walls up. And I get it. I've been there and done that very thing. I had walls up for a while. Heck if any guy tried to talk to me I was most definitely sassy back and closed off. But that's not fair.
See also: To The Boy Who Showed Up When I Wasn't Looking, You Showed Me Everything I Didn't Know I Needed
I'm not telling you to not guard your heart. No, guard your heart for the world because it is so precious. But you can't live life automatically placing the same judgment on every boy solely based on your past broken relationship. You can't approach every new conversation with a boy closed off and already believing they will hurt you. Because if you do have that pre-conceived notion already, you might miss out on a different boy.
You might miss out on a man.
The boy who keeps his word and proves it in his actions. The boy who lifts you up, encourages you, inspires you, and never ever makes you doubt. The boy who makes you want to tell him everything.
If you're too busy worrying about each boy hurting you, you may miss out on the one who never stops loving you.
Live life unapologetically. Guard your heart, but open yourself up to new beginnings. New friendships. New opportunities. Stop letting one boy ruin it for the rest.