A good mood/satisfaction
Regarding characteristics of pleasure &amp; pain, MN 44 says this:


  Pleasant feeling is pleasant in remaining, &amp; painful in changing, friend Visakha. Painful feeling is painful in remaining &amp; pleasant in changing. Neither-pleasant-nor-painful feeling is pleasant in occurring together with knowledge, and painful in occurring without knowledge.


Regarding your sleepiness: once the need arises, I'd try to substitute some of it for meditation, trying to focus on the breath, and not go anywhere else in your mind. Just sticking with it.

If you can get yourself to a state where you can enter meditation and gain refreshment and enjoyment, you'll have made very good progress, and that choice will now be more readily available to you wherever you are. But like anything worthwhile, it takes persistence and dedication to attain. So try to use this motivation for rest that you have right now as a catalyst for developing good qualities.