So you buy kind of a crappy car that works okay but has already broken down on you more than once.
You put a lot of work into it and decide to drive to see a friend.
The first hill you come to, it barely makes it.
The second hill, it dies on the side of the road, but with some coaxing you get on your way again.
By the time you get to the last pass, you're out of gas, but you can see the your friend's house in the valley.
You knew you'd run out of gas or something would break down eventually.
Do you sit there gazing wistfully at your friend's house, or do you walk there until you can get your car towed?
You're probably going to scrap that thing, anyway!
The trick for me as a fellow brain-fogger has been in not relying on fabricated motivation or changing moods to determine everything
I only recently noticed how obvious it is that practices based on causes, like choosing to cultivate mindfulness or metta, will eventually dissipate when their causes also dissipate. Darn it, dropped my damn desire to save all beings again!
How much more unreliable is a vague feeling like motivation?
That's like your car crapping out on you... but you still have two perfectly good legs for walking.
For me, the value of practice is in finding my legs again, not in somehow making shiny new Dharma legs that I slap on there like the bionic man
And anyway, since you're not trying to condition some brand-new, better you that will fall apart when those conditions also end, what's actually driving the procrastination?
See if you can suss out the subtle dissatisfaction behind this lethargy or boredom (First Noble Truth).
Notice how it leads to searching for "something else, a better time later" without ever providing real peace or only temporary respite (Second Noble Truth).
You've already seen how when those feelings are absent from your absorption in exercise or getting a jump on work, their attendant suffering is also absent (Third Noble Truth).
And you've doubtless seen how the Dharma provides not only an analysis of what's going on, but skillful means to help your suffering, big and small (Fourth Noble Truth).
You're really doing a lot better than you think if you have the self-insight that your post shows.
As someone who also can succumb to chronic fatigue or paralyzing mental torpor, daily meditation is vital.
So if you really are too tired and want to drop everything, at least keep daily meditation, as simple as you want to make it.
It doesn't have to be big or fancy, or particularly Buddhist. You already know how to just be aware... that's how you know you feel foggy or depressed in the first place!
If you can become intimately familiarized with your ups and downs, you can start to get a sense of how the mind illuminates and recognizes those states effortlessly, and remains uninhibited by them.
In this way, energy, brain fog, procrastination, are seen for what they are: conditioned things that you're aware of.
Beyond that, to the extent you identify, then to that extent you're hindered by unideal circumstances, and are necessarily dependent on these tricky, complex phenomena to turn out a certain way for you to practice or be happy.
Sounds like a gamble, doesn't it?
Hope that was remotely helpful