Do you ever think about this?

I sometimes regret not giving some people a chance. I remember how cool she was. I remember how well we got along. I remember the signs she would show me and the signs I would show her. We used to have such a good time together. But for some reason, some strange subconscious reason. I didn't tell her how I really felt about her. It wasn't fear of rejection because we both new how much we liked each other and we would hang out almost everyday. I knew she was into me but at the time I felt like I wasn't capable of maintaining a relationship. I feel like I'd burden anyone who gets close to me because I have so many flaws. I believe this is the reason why I refused to give myself up to her. I don't want to bring anyone into my mess. Things never really get past the flirting stage nowadays because I don't know what its like to let someone like this into your life and its kinda scary. I see everyone else's relationships breaking and I've seen some strong ones break too like my parents so is it really worth it? Do all relationships fall apart naturally?