I figure this happens to all of us, so may as well have a thread.
British, romance/drama, the hero (and members of his family?), can send his consciousness back in time for example replaying a day with the advantage of hindsight. But he learns after he's married and had kids if he goes before the birth (conception?) of his kids his kids will cease to exist. Time travel means different combinations of sperm and eggs and different kids.
Saw it on a flight a few years ago, so maybe from the 2020s or so?