Some can. Some can't. It seems your friend is in the "can't" category. What's really happening, I think, is he's changed as a person. Which means the way he sees you and others has probably changed. What applied before, doesn't apply today, because he's changed. He hasn't done anything wrong, because everyone changes. But...it changes the dynamic of your relationship. Unfortunately, we only have the ability to change ourselves. This means you are stuck in a position of having to take, or leave, relationships as they are. I've ended long friendships in the past five years. And others, who I thought were my friend, have ended their relationship with me. It's normal, because people change and their needs change. It's easy to look in the rear-view mirror at what was, but it's not helpful, because you're not going backwards. Returning to a past point in life may be appealing, but it's not going to happen. So you can set clear boundaries with guys who want more than friendship when you do not. And they will definitely reveal who they are when you do it. If they leave because of it, you are better off. If they stick around, you still need to make sure they are aware of the boundaries. If they stick around in the long term, great. If they don't, great. It really comes down to being true to yourself and your feelings and accepting whatever happens after that, even if it means losing a "friend."