If you do not use the boat to pull the weakened fish through the water for at least 10 minutes, the oxegen required to revive the fish is not present.
So for the larger fish and the weakened fish, you must move off your spot to revive the fish and then reset your lines.
If you just drift and try to revive the fish, it will not work.
The best way, is to leave the hook where it is (unless it is easy to get out) tow the fish by the leader (or use a snooter) then cut the line close to the fish.