It's taken years, but I've now gone about two months without the consumption of soft drink.
I've experimented with other habits during that time also; daily prayer, pushups, squats, giving up swearing, etc. Most of them have continued but not at the level of success I have had with giving up soft drink.
I've also picked up some new things. Drinking coffee is an example. Some habits are easily acquired, but are hard to break once established. Developing good habits is necessary to improving oneself.
I'm no expert, but I think it begins with the elimination of one vice (or conversely, the development of one good habit) at a time. This was something I remember learning from Thomas A Kempis. We can make good progress if we eliminate one vice from our lives each year. If we were to eliminate two or three per year, that would result in exceptional improvement in our lives over a decade.
What vice are you currently working on eliminating?