I've only been training a couple of years but around the six month mark of training in Aikido, I started having to force myself to go to Aikido. I almost always enjoyed myself when I got there, but talking myself into going was tough.
I was resentful of having to account for when I trained. If I didn't train a night when I usually would, my roommate would pester me about it; the next class, everyone would ask me where I was. I hated feeling so monitered. I was resentful of other people feeling that they had the right to make me account for everything I did. That particular feeling has gone away now that I've practiced more and think of nearly everyone in the dojo as my friend.
I still feel guilty, though, if I don't go to class on a night when class is offered or if I go less frequently than usual. Usually I feel the most guilty when I'm doing something I deem "recreational," like non-academic reading, hanging out with my friends, or watching a movie, etc. Although I know that we all need balance in our lives, I still feel guilty about taking days off when I could be applying myself to something more spiritual, noble, and valuable. I guess it's good to realize that I nowhere near as developed a person as I want to become!!