It's like depressive thoughts and feelings at ten times the speed and all the energy in the world. You have the freedom to do anything because absolutely nothing matters, even life itself. Have a thought in your head? Go for it, not because it's an experience or it feels good, nothing feels good and consequences don't matter. There is no reason to do or not to do anything, but you do anything because you can't sit still even though you want to. Screw yourself, screw your neighbour, screw life, screw it and you've got the energy to do so and more time too 'cause sleep isn't happening. It's like being angry all the time and just waiting for any excuse to blow up when normally you'd laugh it off. It's like every sight, sound, taste, texture, experience is an enemy and you're preparing for war or death, you know, what ever happens.

In doctor talk? It's a combination of manic symptoms (racing thoughts, less need for sleep, impulsivity etc.) and depressive symptoms (hopelessness, intense saddness, suicidal thoughts and feelings etc.).