I definitely have trouble with this. Not just in therapy, but whenever I'm talking. I usually say things like "good", "bad", "nice", "cool", etc. Later on if I think about it, I can think of better words, but when I'm speaking to someone it's hard for me to name my feelings. Once in a while I am able to think of a more descriptive word, but then I'm usually too embarrassed or nervous to use it.