You should try lifting some weights. Write down the exercises, sets and repetitions every day you train. Keep at it and you will see massive progress both mentally and physically. Especially at the beginning, you will progress so fast you will look a couple pages back and see how far you've come.

Even if it was not on list of ideas, and you could consider it not a "real" goal, surrogate activities like finishing a book or doubling the weights you lifted last week could help you feel a sense of accomplishment in these dark times.