Disclaimer: I'm no expert on any of this whatsoever, I just say what kind of works for me.

First, make sure your body has enough nutrition. For me what helped most is to primarily focus on protein. Because I already know that too much sugar is bad, the next thing is protein. And the funny thing with protein for me is, the protein LED warning light on my control panel is just next to the sugar warning light, so when I'm low on protein, it feels a lot like craving for sugar.

Fat is another question but personally I don't bother with it too much. That one just kind of becomes sense. Depending on where you live, most things that contain significant amount of fats are either highly processed foods (which you should avoid anyway) or things that also contain protein.

Second, a huge part is sleep. Nutrition is great but it goes to waste if you don't sleep enough. Lot of things that your body uses all that expensive "fuel" for are happening during sleep.

Personally for me, tracking sleep kind of helps, esp. if I feel depressed, then seeing the stats can help me anchor my mood back to reality. The depressive thoughts and ruminations tend to be heavily speculative, so It helps to add a little bit of fact into the inner dialog. Like "Look maybe we really are a failure and a bad person and a worthless piece of *. Maybe. We'll never going to be sure but it's possible and it could explain our current mood. But the other thing that could explain it is also this cold hearted, undeniable fact: we only slept 12 hours of total for last 3 days, sooo.... choose your adventure". That usually helps me to choose to go to sleep and the next day i just feel much better, the "demons" are much much weaker already.

In case you tend to ruminate instead of falling asleep, well, having enough physical activity helps a lot, but other than that, my 2 most powerful tools are physiological sigh (look it up) or "what's next" meditation: all that is that if i catch my brain ruminating, I try to "ask" it what's the next topic of rumination. Really, just ask a question with curiosity: after we finish this, what's going to be next. It works surprisingly well.

My naiive interpretation of why it works so well is that maybe my brain is not all that super interested in the ruminations in the first place, especially if i remind it that ruminations are speculations, which can be useful but---not unlike salt----only to small extent. Maybe it's kind of just doing it because it's bored and unfocused, so by asking this "what's next" in an honest way, it will kind of stop and say "umm, interesting, i don't know" and start looking into distance. (Here being OK with saying "I don't know" might be really an important piece.)

Final thing that helped me is to never allow myself to get dragged down by failures to keep up. Sure, skipping for "wrong" reasons (such as forgetting, or just not feeling it[tm]) is bad and all that, but at any point in time, 90% of the win is here: am I going next time? I mean, even if you skip for a year, schedule a next training session and try to focus on getting your a** there.

If you fail to go, just repeat. Don't let your inner demons convince you that just because you have skipped for "oh such a long time" you are somehow not fit for getting fit. That's just bollocks and the thing is, if you starve your brain of the other things it needs, it's more likely to go into this depressive mode which tries to use every trick in the book to convince you not to do anything. It's worth noting that yeah, depending on how deep you are, going from that point to a better point might need to feel like a leap of faith -- that's expected.

Again, there are legit and important situations when you should rest, and but if you're like me and tend to fall back easily on the nutrition and sleep side, you can bet that 90% time if you encounter these toxic worries and ruminations, it's because of these purely technical things for which you can actually make very concrete actions to start improving.