I recently started a new small-steps habit — two minutes of breathing exercises with a resistance device, to help increase my lung capacity.
For the first couple days, it was tough. I got dizzy a few breaths in, and had to stop and breathe normally multiple times in order to get through the exercise.
Then my lungs started to adapt, and it started to feel good. All that oxygen rushing to my brain made me feel perky and alert.
I started doing it twice a day, once in the morning after I journal, and again in the afternoon, when I hit that afternoon slump. My energy levels went up. A lot.
Then I quit.