I have proven to have enough self-control to make several big improvements, for example, my diet no longer includes certain junk foods. On the other hand, I still have some bad habits which need to change ASAP. How do you create good habits and break bad ones, what actually works?
What you consume or fill your minds with always (whether things you see, hear, think, words, foods, drinks etc), and find acceptable, will form your behavior and move you to act or behave in certain way... Or rather,
you are what you consume. The more you consume something you like the more control it has over you and your body would get used to it and want it always.
Find good things you enjoy or good things that make you happy and consume them always. Your body would crave for the good things when you stop consuming them.
To break bad habit, stop consuming the bad things (whether words, foods etc) that caused the bad habit and forget about them. Replace them with good alternatives you enjoy. Consume the good always and it will form your new habit/behavior.
You develop "self-control" when the good things you consume(while avoiding the bad) have made you strong enough to resist the bad when you come across it in your mind, with your eye, ear, etc, ... it's basically the good things strengthening your body and becoming resistant. That why it's important to consume the good always.