Here's what I'm doing, maybe it will show you a path to success.
I've tried many times, oh so many times, to get FIT. I've had some moderate success and then bombed. Over, and over, and over. However, I'm always tweaking the formula and getting better each iteration. This is the documentation of iteration 20 or so, and going on until I get bored! If I succeed, you'll see how I did it and maybe it will help you too.
I did my first 100 pushups (one of my new habits).
This was after Judo practice where I'd already done several pushups. The first day was 10, 12, 7, 7, 9+ pushups for a total of 45. It was hard but I did good.
I'll periodically report my progress towards 100.