Have you tried listening to music? Something calming, maybe. Or get really angry at the world or anyone/anything and express that. Go outside where there are no people, just walking, maybe running.

Be safe! You can be. There are substitutes for self-harm. Or do it long but very, very mildly. Depending on your impulse control this can work.

Imagining is not doing. Don't fight imagining or it might turn into doing. Think about how you imagine, then how you think about imagining and so forth. Observe and think about how you feel, just that. It will distract you.

What goes up... (edit: same for affective and non-affective psychosis)