Is there a way to instantly end the current loop?

If something goes badly awry and you can't find a fast enough method of killing yourself, the game provides two mechanisms by which you may instantly end your current cycle.

On Giant's Deep you can locate your fellow traveler Gabbro. During your first conversation with Gabbro, they will talk about the time loop if you have already died at least once; if this is still your first flight from Timber Hearth and you haven't died yet, they'll instead talk about the experience of pairing with the statue over on Statue Island. You will need to return to Gabbro on a later loop, which will give you the option to ask about remaining calm in the face of certain death. Gabbro will offer to teach you meditation. (Note that accepting this offer will end your current loop, so if you have other stuff to do on Giant's Deep, you may want to come back close to the end of the cycle.)

If you haven't learned to meditate and you find yourself in need of a quick death, you can still quit to the title screen. The game warns you that your progress in this loop will not be saved, but so far I can find no evidence that this is actually true; every time I've done it, my log entries from the loop in which I quit were still available after I loaded the game again.

Gabbro on Giant's Deep can teach you meditation, which immediately ends your loop. You can find him by listening for nearby signals when you get to the planet. He's on an island, swinging in a hammock near a campsite. Look for a plume of smoke.

I'm not 100% sure what triggers him teaching this to you. The first time I found him, I talked to him about how he also experiences loops, but I didn't see any option to learn meditation from him. I talked to him again on a later loop and asked him something like "How do you stay so calm when you know we're going to die?" and he taught me meditation (which, by the way, immediately ends that loop for you when you acquire it).

Meditation can then be accessed at any time from the pause menu.