I can relate. It was such a difficult adjustment to accept that this illness blocks who you are, willpower is not an option and only by taking it one day at a time it is possible to heal.

I am now treating my depression like a chronic pain, this means I am pacing myself accordingly. Discovered my base line of activity was 4 hours, so I cut my activities in half, and have been adding 15 mins on the day each week. Even when I do not feel energised I attempt to meet my goal. Now is 2.5 hours. The theory is my adjusting slowly I will be exceeding my 4 hour in no time, and in this way controling the depression not having it control me. Flare - ups with chronic pain are not damaging but signal to the body to be more sensitive, so avoiding flare-ups helps the mind/body heal or cope to maximise the quality of life.

When I am feeling the return of energy, I continue to limit my outside activites, so that I do not trigger a flare-up, that sends me back in bed and in the pain of depression symptons.
I am now on day 7 of feeling like the medication is finally working,(after more than a year) and I do not want to set myself back by doing 7 months work in 7 days. Before I found pacing I did bring myself close to breakdown by overworking the "good" days.

I am also fluttering at www.flylady.net . On the days when it is too much to think, I just go to my morning list as start doing, without having to think, it works most days to jump starts the activties.

Glad you celebrated having a great day! Wish you many more.