My immediate response is frustration/anger and despair as I see the gap between what I want to do and what I can do. Sometimes that can make me feel anxious, which will only increase my heart rate. That's the last thing I need.
So I sat up in bed, turned on some worship music, and repeated to myself, "I am not the product of my works. What I do today will not change my worth."
For me, discontentment always comes when I get too focused on what I wanted to do. It's easy for me to start having pity parties about what I can't do, but then ironically I often miss out on the smaller things that I can do.
So I took it really slow and started feeling better as the day went on. At the end of the day I didn't accomplish all I had hoped, but I still managed to accomplish a number of smaller tasks. And that is what I need to focus on and celebrate.
To keep myself grounded, throughout the day I kept repeating to myself - "I am not the product of my works. I am who I am, regardless of my achievements." No action or achievement can change my worth as a person.