Well at one point in our life we've reached a series of negative events that changes our entire way of thinking but when that happens don't let that get you down. You'll live through it and you know that you're still alive when you still feel because I've been through such events where so many people betray me and a few where I betray others but you should know from all of this pain: don't fear relationships unless you don't feel anything anymore- pain included. When I look back to those events, it's painful but it's okay to think about it because although those are scars they aren't going to happen again.
Learn from those painful experiences to become a better person, try to be confident about yourself, and make sure to tell that person what you fear the most- and if they don't take understand that, then they're not the right one for you yet. We go through these stupid cycles of pain because we haven't learned for ourselves what 'pain' is yet since being a human is where you take tedious steps to learn how to love yourself and learn to love them through various relationships.
Also another note: don't fear the future, focus on the present. What I've learned is that humans always think black and white: past or future, hate or love, etc. but there won't always be two options- you need to realize that if you only focus on the future or the past you'll only be hurting yourself and the ones you love more. Focus on the present and laugh through it, cry through it , but do it with others because that's what makes the present memorable.