Sean
Let's just use a hypothetical situation. Let's just say that I realised that I had feelings for, I don't know...you Charlie Weasley (I don't but he's a good example to use) and I knew that a good friend had potential feelings for him. The hurt that you feel when you have feelings for one person and someone else that you love does as well is just too hard to deal with. Because I'd always choose my friend's happiness over my own.