I suppose the worst thing that people do is to take others for granted. But, I can look back on my behavior towards my wife and kids and easily say that I took them for granted. I see that now that I am not in a position to be around them all the time.
I suppose I took all of the time that I could have been spending with my kids for granted. I can't think of the number of times I was tired after getting home from work, and I turned down an invitation to "come play" with my kids. How many times could I have sat and played with them instead of laying down for a quick nap.
I also look at my relatioship with my wife and wonder the same thing. It is just amazing to think back on the number of times that I would be in my own world, doing something I wanted to do instead of talking to her. It is so easy to read a book, watch television,