Slow and steady.
You can’t do it. You’ll never finish. It’s too hard. You need help. Might as well paste the “L” on your forehead now—you’re nothing but a big loser.
Hey, hey, hey—that’s enough of that. You’re going to talk yourself right into therapy. What you need is a little pep talk: You can do it, whatever it is. You will finish. You just have to break it down into smaller steps.
Let’s say you need to clean out the basement. Totally overwhelming. But now break it into individual tasks—literally, make a list—like “clean off table,” “break down boxes,” “vacuum cobwebs” and so on. Today, do the first item. Tomorrow, do the next one and so on. Pretty soon, you’ve got the whole job done.
Slower than you might have liked, but way faster than doing nothing.