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.
The first method, available to everyone at any time: open the pause menu and quit to the game's title screen. The game warns that your progress will not be saved. While any updates to your ship log will persist, you will resume playing from the start of a new loop.
If you'd prefer something more diegetic that skips straight to the start of a new cycle, find your fellow traveler Gabbro on Giant's Deep after you have died at least twice. (Gabbro's island is the only one with smoke coming out of it; you can also use track his flute-music using your signalscope, or if you've met him before, mark him on the rumor map.) If you've talked to him in at least one earlier loop, you'll have the option to ask him how he remains so calm in the face of repeated deaths, at which point he will offer to teach you to meditate. When you accept this offer, the current loop will end. You will then permanently unlock the option to meditate at any time and jump to the next loop.