Set up your phone's own Focus mode or app limits first (see the Blocking tab), so the apps that pull you in stay quiet.
Ending early takes the code on your unlock card.
Ending a session early takes a code you keep away from your phone. Write it on a sticky note or print it and put it on the fridge. The walk over is the point: by the time you get there, the urge has usually passed.
A web app can't lock other apps, but your phone can, for free. Set it up once.
iPhoneWhy bother? Every switch costs your brain time to get back on track. More on deep work.