There is one aspect of fitness that requires minimal training--running. Running is one of the most therapeutic forms of exercise. It has proven to have a direct effect on our brain. It is a direct connection between the mind and the body.
While doing other exercises, you have to learn the technique, focus on doing it right, etc. But when you're running, your mind is not as occupied. And this makes it harder to go on as your mind will make any excuse to stop. But you have to steer through it and keep running. So no matter what pace you run at, the run will do you good.
Every time you try to push a little, your mind will tell you to stop and that you're tired. Your first 5km run or even 1km might seem like such a big challenge. But you push your limit every time you run. So tell your mind that you're one step ahead.
There will be days that you might not have good runs. But don't let that demotivate you. Sometimes, it takes two steps backward to go four steps forward.
When you finally achieve your goal, you will be shocked at your potential. Running will help you unlock your true potential. There'll be a new version of you emerging.
You don't even need to run marathons or be an athlete to start running. You can wake up tomorrow and run. Anyone can run. If you're a beginner, don't be scared to start.
"There is something magical about running. After a certain distance, it transcends the body. Then a bit further, it transcends the mind. A bit further yet, and what you have before you, is the soul" - Kristin Armstrong.