I found that slow increases help me best. Running, weights. I increase a little every week or so, so that I don’t really notice the difference by the end.
The best way to keep endurance is by planning ahead. Make a to do list of things that you wanna do and you’ll feel happy everytime you can check a task of your list, make plans with a friend to workout or clean up together. For me it helps to talk to others about my plan and write out all the things I want to do in a day.