Sometimes without thinking we can make others uncomfortable, or feel what we contribute is not important. It is usualy done accidentally, but, it can still hurt. At some point I suppose we all have done this unintentionally, but it sticks with the person sometimes for a long time. It can make things that once were fun, not so or can make you stay aloof to keep from feeling like you dont count.
Friends sometimes dont think, before they ignore, then later wonder what happened. We all try at some point to become important in what we do, and when that is not felt, it leaves a void, one very hard to fill. Many times at that point, its better to stay away, than to be ignored.
Its hard to always know what is expected, even harder to see what you do being changed or taken. It takes the fun...or the smiles that once came so easy. Maybe, if we all just slowed down, and put ourselves in others place, we might understand this. But then, maybe that is just to hard.