Push to your limit, then keep going. The anxiety you are feeling is growth.
I was fighting with the treadmill with this morning. An hour straight up a hill. Forced speed and incline will push my heart rate over 160-180. Then I ease off until it comes back to 150 beats per minute.
Tough stuff. When I felt like quitting, I pushed a little further. 1 min, 2 min, 5 min.
In the desert, it may be an hour or more. What you do in practice come out in life.
When you hit that resistance today, keep going.
The kick in the pants you need. Sign-up for a better start to your work day.