This is one of the most common questions in pedagogy. Sometimes it reflects a lot of anxiety.
This question is similar to this one: how to be healthy? It’s quite obvious that there is no straight answer. There are lots of things to do in order to be healthy. You need a good hygiene. You need some good daily routines, like enough sleeping time or a well-balanced diet. You may need medications sometimes. If one of your organs fails dramatically, you’re dead. It doesn’t matter if you loose your brain, or your liver, or your heart, or your kidney. The result is the same. Your need all of them in a correct shape.