Numb....

There are times when I sit down and wonder why? Why is it when life becomes good there is something bad that comes and destroy that good life and turns it into something terrible.
My heart has been broken many times. Not only by boyfriends, but just people you called friends in general.
Sometimes i develop certain connections with the people i become involved with, but other times i only allow myself to get but so close....
why is that?
When i am done talking to that person that i decide not to get too close to, I start thinking that there is a reason behind me not getting as close as i could have...
is there a reason for everything...
for example, me and this guy start talking, but mentally and emotionally i am kinda distant from him. this is a guy i could have had strong feelings for. no doubt i liked the guy alot, but i would not allow myself to feel so deeply for him. next thing u know something happens. it could have destroyed my heart and hurt me bad, had i gotten closer to him on that emotional level. Because of all of the pain i have endured by the no-goods, i sort of developed this mindset of not catching feelings for the ones i become involved with. this is done unconsciously, i do not try to make myself feel this way, but i do.
So when he did whatever he did, that could've hurt me, I couldn't even get mad. i couldn't cry. i couldn't even show as much emotion as i wanted to. i could've cursed him out and everything, but something inside of me wouldn't let me.
It was as if i was "Numb" to the pain.
Ok. so i was numb to the right person, but there are times when i catch feelings for the wrong person. deep down i know that person isn't for me, but something keeps pulling me closer to them, and i develop those feelings that i usually don't have for other people.
When i do talk to that person, i feel good, liked, loved, and even safe. But then right after i see that person and it seems like we are off to a great start for the billionth time, i go back to not hearing from him again. why is it that we want something that we will never get?
The reason i say i will never get him is because he has proven to me time after time he is unreliable. Unpredictable, because he could start off calling, but then go weeks without talking to or just communicating to me period.
So again, why am i not catching the "numb" feelings for this one as well? why do i have these feelings for him, but he means me no good? why is it that i get these cold feelings when it comes down to me being hurt?
i don't know, maybe it will be just what my family and friends tell me. I might start trusting again once that right person comes around.... i don't know...... somebody help me understand this!