I am glad to read that, anon, and wish you well.
This is in fact the same thing that happens with human relationships: a lot of people feel bad for being "bad friends", "everyone secretly hates me and just puts up with me out of politeness". I have never struggled with this, but I know people who do and it's the same principle.
The commissioner isn't demanding you to be a better artist, the friend isn't demanding you to be a better friend, they are there because what you provide already suits their needs. If you improve, everyone wins, but you're the one who's demanding improvement, not others, and this is very liberating, in a way.
Also, it's easier to give advice than to follow it, I myself struggle with procrastinating work.
And I've come to realize it's all self-inflicted, the commission I'm currently putting off is not just my usual illustration, it's an asset to be used officially in a game that will require my best-looking artwork to measure up to the other assets, and I was even asked to try to imitate a bit of another artist's style.
I shouldn't have accepted it, or at least not accepted the part where I have to imitate someone's style and see if the client would still want my work anyway.
Good luck to us.