When practicing mindfulness, enjoyable mental states can be just as challenging as unpleasant ones.
On the basic level, there’s grasping and attachment. Something feels good, and you don’t want it to end — pretty understandable. But this is a practice of deeply understanding and accepting that everything ends. The way to practice that is to let it happen, even if it hurts. After all, in your life off the cushion, it’s going to happen whether you let it or not, so exploring that feeling in meditation is practice in the truest sense.
Sometimes mental states aren’t just pleasurable, they’re productive, and this brings the challenge a level deeper. Letting go of a nice feeling hurts, but another one will come along soon enough. Letting go of a state in which you feel like you’re accomplishing something or getting somewhere can feel downright destructive.
When I get into a creative state of mind, it’s like a magician pulling multicolored handkerchiefs out of his sleeve; each idea pulls out another idea, and another, and another. Sometimes it gets ridiculous. There’s often one or two good ones in there, though. It takes every fiber of my being to let them flutter away while I’m meditating. I live on having good ideas. Letting them go feels like dying!
Occasionally, I simply must write down an idea during meditation, so I can calm down and sit again. I forgive myself for that. But the trouble with ideas is, not all ideas come to life, and being creative requires accepting that. This practice has got to involve letting some creative darlings die. When a good feeling goes away, it takes faith to believe another one will come along. Creativity requires that same faith in good ideas. Practice ideas during productive time. Practice faith during contemplative time.