I go to the pool

The spring is coming and I've decided come back to the pool everyday. It's hard because I get up early in the morning and go to walk about an hour between the rice fields. Of course currently they're dry but soon they will open the river doors and the water will flood the land.
When I arrive to the pool I feel tired but I need to do it if I want to take care of my body. I swim 80 pools which it's about one thousand metres. 20 minutes changing crawl with breast-stroke. Not bad.
I leave my pool and come back home walking as fast as I can.
If I want to change my mind I need to do it along 21 days. After that, it will be a routine and everything will be easier.

  = what I changed. You use at when it is specific like when you use hours. When not, use in for general/ bigger time. You use make when you create something and you use do about an activity.

   = what I added. If you do not put they, it sounds like the rice fields will open the river doors itself.

  = I thing it sound better.  You said in beginning that it is being hard, so it sound better if you say that it will be easier.