New habits require new connections in the brain and this requires conscious effort. The brain is capable of working subconsciously on automatic programmes. For example, you do not have to think consciously about which muscles to move, when you decide to reach out your arm. When such programming is irrational, inappropriate behaviour results. To learn to sing, play an instrument or think with a trained mind, and to do this with above average ability, requires hundreds of hours of practice, normally in the form of practical exercises or drills.
Modern education neglects drills.
Mostly it consists of grasping a principle in a stumbling sort of way. This becomes the shaky foundation of the next thing to be learnt but after few weeks, the structure falls down like a house of cards. Outside of music, sports and the military the concept of overlearning has been all but lost. In the army a lot of time is spent taking a gun to pieces and reassembling it, until this can be done blindfolded in an instant. In learning to play the piano, scales are repeated thousands of times.