You can forgive your friends for anything. Whether it is for literally inhaling that last piece of chocolate you asked them to save for you, or even for stealing your girlfriend. But you can't forgive them for spitting on your dreams.
It's just sad when that happens. You feel like they don't respect you or what you aim to do in life. They can't provide you with the motivation you need to keep steering towards your goals. From that point on, you don't feel like sharing your joys and successes and eventually the friendship wears off.
I guess that is just normal in life. Good friends come and go. After all, you need to have perfect understanding and friendship with just one person in this world.
That elusive one.
If we're lucky, all of us will find that one, get married and have hundreds and thousands of (hypothetical) kids.
Of course, most of us are jinxed.