First change your identity, then change your behavior.

Think of yourself as a lovable person, a good-looking person, a capable person, a sexy person, a thick-skinned person, a smart person, a person who loves to learn, a disciplined person, a great person.
Keep thinking this way about yourself, often think this way, and keep thinking this way continuously. Once your sense of identity changes, good behaviors will become increasingly effortless.
Your real lesson is to keep thinking like this, over and over again.
After the neural pathways corresponding to your thoughts undergo physical changes and become sufficiently thick and dense, it’s like installing a new high-bandwidth fiber optic cable in your brain. These thoughts will become your conditioned reflexes, and you won’t need to practice deliberately anymore.
So where did the original negative thoughts go? The principle of neural pathways is use it or lose it.
When you think negative thoughts less often, the neural pathways carrying those negative thoughts will gradually weaken and disconnect. The synaptic terminals between neurons will slowly be pruned, as the brain doesn’t maintain idle neural pathways.