I used to be very embarrassed to modify the workouts in class that I do. I felt like the "bad student" or the "cheater" because I wasn't doing it the way the instructor was asking us to do it.
However, now I modify as I need to because only I know what's best for my body. Sometimes that means wall pushups, or it means having my feet down doing ab work instead of over my hips. I'm not trying to cheat. I'm just trying to keep my workout from hurting my body and even keeping me from hating it.
For instance - Dips. I hate them, mostly because I can't do them. My triceps just can't dip my body weight. So I do overhead extensions. It's still a tricep workout. If I keep trying and failing at doing dips, I'm going to get so discouraged that I'll throw in the towel. So I modify. I do what is going to keep me going. Because if I get injured or burnt out, then no good can come from that.