Everything I am about to say is likely inapplicable to you because I have a low threshold for energy that is part of a condition that won't go away through retraining my muscles. But I am going to say it anyway because maybe it won't be inapplicable!
I have found that the toughest part about this is keeping from getting overexcited and overdoing it. It can be frustrating in the first few steps to just do a little bit, and then just a little bit more. This can be more a thing if you are doing an action that has more to it than just physical movement. Like, I often would try to go beachcombing for seaglass, and then on some days I would not find much at all and feel like I should extend my walk so I don't come back disappointed. Which just ended up exhausting me and forcing me to rest long enough that I lost any benefit of the workout.
I would say that a smart thing to do would be to time your workout, and even have a little alarm go off when you are done. And of course, you just slowly increase the number of minutes, like if you can do 10 minutes, you try for 15, or if that's too high, somewhere between there. And generally the longer you can work out the longer the increased increments should be. You really should try to stick to these times, and not convince yourself that you can do more than what you have decided to do, at least during the workout. If afterwards you reflect on it and decide you can increase your workout time, go for it, cautiously.
But basically, don't be impatient. It's a slow, long process.
that makes absolute sense for me! patience, caution--i have trouble with these, especially on days where i feel i have some energy. i always seem to forget that a faster workout does not mean a faster recovery, and always seem to push myself too hard. so slow, steady, patient.
and if it's not too personal to ask, what kind of condition is it that you have that leaves you exhausted? it sounds a bit like something my little brother is experiencing at the moment.