This is personal opinion and nothing more.
Just as there is only one God in three persons: Father, Son and Holy Ghost, and since God created us in His likeness and in His image, we too are three in one: Mind, Body and Spirit(Soul).
We lose our body when we die, but our spirit and mind keep on living.
We can lose our mind, go insane, but we still have our body and our spirit.
We can exercise our body and grow our muscles. Likewise, we can exercise our mind and grow, and we can also exercise our spirit and grow spiritually.