Yeah, I see what you mean, shelton. When I practice solidly every single day, I sometimes lack motivation, but when I'm away from the keyboard for a few days I really want to play it again.
I usually practice the piano every day, though I tend to miss out about a day every week. When I practice, it's normally for about 30 minutes to 45 minutes, though sometimes I do it in snippets (like 3 times of 10 minutes each).
Now as for that clarinet... haven't touched it for about a week now. Oops.