I was hospitalized last fall for a manic episode with mild psychotic features. During my time there I found the more I wrote, the more stable my mood would be. It was a way to ground myself in a place and time that frightened me, because I knew that depressive crash would come eventually.
It took a lot of pressure on myself to keep it up when I did drop down, but I kept writing. Not novels or huge bodies of work, but enough to get out some of the negativity building up. It got me through in one piece. Your ability is ALWAYS there- mania or no mania. Sometimes it just hides from you.