What do you think ends a three year friendship?

Suddenly we’re not friends anymore. I don’t know what I did wrong or what happened. We said we’ve meant a lot to each other and that we’ll always be friends. It felt like over night a decision was made to just end it. We haven’t talked for like a week before it happened. So I don’t know. :/ Do I talk to you about it? I don’t know how much you mean to me anymore…