Why do people ignore you and how do you deal with the situation?

Hello,

people usually have a lot of reasons to ignore us. They are in a hurry, we have hurt them (and we sometimes don't know about it), they really didn't see us, etc.

The next on my being-ignored-by list is a colleague of mine I used to be friend with. Maybe he is having quite a stressful time, maybe our friendship was growing too much for him, or was it something I said? I don't know. I should be getting used to it by now though as it's not being the first time he pretends I don't exist.

I feel a little confused and hurt as I considered him a friend. He had been there for me at a really dark time (I lost my dad earlier this year) which is why I thought we were friends.

I don't think he has ever wanted to date me : both of us are not single! It is just weird to have a friend who hugs you one day and absolutely doesn't want to talk to you the next day.

How would you deal with that situation? What have I possibly done wrong?