Many, many years, I read a piece of advice - I can't even remember when or where - that suggested the strategy that when you stop writing, stop in the middle of a sentence. The logic of it is ... then when you return, you have a platform to start from. For those who write by the seat of their pants, there's always the fun that the sentence may go in a different direction than intended, too.
I decided to try this out. I found it really worked for me. I can usually recapture where I was going and it makes it just that smidge easier to bound back in. Every now and again, re-examining the previous paragraph elicits the response, "No, that wasn't the start I wanted," bt the process still offers forward momentum.
To me, it's not just about stopping for the day: if I pause to get a glass of water, pick up the mail, run out to handle an errand, I always hang in the middle of a sentence. I've also found it works best not just in the middle of a sentence, but in the middle of a clause - truly in the middle of the thought.
For those who counter that they prefer to write until they're entirely out of steam ... well, if you do this long enough, the energy pattern starts matching it. ;-)