One of them which sticks with me is about fighting addictions and habits - every time you win this internal fight (go do something unwanted, don't light up that cigarette or drink alcohol) you get a bit stronger and addiction gets slightly weaker. Same for habits and defeating procrastination.
The hardest part is the first step, when opposite side (in your own persona) is strongest and it feels its too high a mountain to overcome. With addictions you never chip it away to 0 - that's the unfortunate cold hard truth, but you can chip it away into something you can manage continuously. Good habits are often self-fueling after crossing some threshold, ie exercise and eating healthy.