The “just” part is the hard part. Ego depletion may not be real (another), but it certainly seems so for myself. Recently when stressed, I made lots and lots of bad decisions earlier in the day than normal.

These tactics are essentially my own strategy for getting in gym almost every day:

1. Chaining: Add it as a step to an existing routine. For me, after work, I go home, change, and go to the gym. The other day, I picked up something from the store and other things to the point the gym was near closing by the time I realized I had not gone. This also makes it a struggle to go on weekends, which I maybe manage one of the two, but the weather has been so nice I sometimes go for an hour walk instead.
2. Precommitment: Making the decision in the moment could go either way. The intentions are better way before the moment. I lay out the gym clothes on the bed prior to going to work, so I’d feel compelled to move them to not following through. (I really do not like the partner example in the post because a friend has flakey partners who often fail to show.)
3. Reward yourself: For me it some bread in the post-workout meal. If I go, then I allow myself to eat some bread. If I fail to go, then I don’t allow myself any.
4. Reduced barriers to training: This is just looking at when I do not go, figure out why and change the environment such that I am more likely to go. And even look at occasions when I almost did not go.