Something I have experimented and found success with recently is setting upper bounds on habits and routines I'm trying to build. I believe I first came across this idea while listening to Greg McKeown's What's Essential Podcast.

The gist is that, along with a minimum, you should set a maximum (amount of time/reps/etc.) when forming a habit. I have implemented this for my habit of writing these blog posts. I have set a maximum time for working on these posts to 15 minutes. When that timer is up, I complete my thought and stop what I'm doing.

Setting an upper bound gives me the stamina to keep coming back to the habit I'm trying to build day after day. It prevents me from overexerting myself.