If I want to know you at all, I want to know you intimately. I want to know what it's like to be you. But that doesn't mean I want intimacy, and it certainly doesn't mean I'm offering any sort of commitment. It's driven by curiosity rather than affection. Sometimes affection happens as a result of that process, if I admire the person, but just as often disillusionment or indifference happens.
Was it your intention to dump this guy completely, or were you just preoccupied with new interests? I get the latter, the former I don't really understand. I can't bring myself to dump anyone unless they consistently behave like an asshole.I may not be able to hold on to people well, but I don't really need to either.
That said, the neediness thing is wearing. And if someone responded in that way (falling to pieces) I can understand why you would pull back. People who need constant reassurance and interaction become draining. It's actually more selfish to lean on someone in that way, despite what people are saying here. Yes, it might be normal, but that doesn't make it healthy. The healthiest way of being, I think, is much the way you are - open with everyone, not burdening them with your expectations and not allowing them to burden you with theirs. The problem (as someone pointed out to me recently) is that being very self-sufficient, one often attracts deeply needy people, who feed off your strength and try to sap you dry. And if you have issues with guilt, sometimes you allow them to do that for too long and just end up resentful and frustrated.