Imagine you are accustomed to walking along a particular path to a set destination. You walk that path every day, month after month, for years.
Naturally the path will be well-worn. The plants that once grew there will have been crushed by your steps and the earth flattened. Small animals and insects would tend to shy away from the exposed path.
You can think of an established habit as a well-worn path in your brain, a series of brain connections formed through performing a particular task or activity repeatedly. That activity is so ingrained in your brain that it becomes automatic; you no longer need to consciously think about doing it.
Let's say you now want to create a new habit to support the aspirations you have for yourself. How do you create new pathways in the brain so that you consistently take the actions you need to in order to produce the results you're after?
To answer that question let's go back to the physical path you imagined walking on every day. This time, however, you want to get to a new destination. Unfortunately for you, that new destination has no path; you'll have to create one as you go along.
And so the hard work begins. You will need to clear away bushes, move aside rocks, and contend with whatever creatures you encounter along the way. This new route is a lot more work that the previous one and you are sometimes tempted to go back to the well-worn path. But you are determined to get to the new destination, so you persevere day after day.
In time you notice that a visible path is starting to form. You see where the grass has been flattened by your steps, the bushes cleared and the rocks set aside. It becomes easier and easier to walk this new path until it ultimately becomes second nature.
Whatever happened to the old path? Because you stopped walking on it, the grass and weeds started to grow back and it became less and less recognisable as a path. You didn't need to do anything to bring about these changes; Mother Nature did that all by herself.
That's how forming new habits works too. Take the actions consistent with the results you want. At first it will be difficult because you are forming new pathways in your brain. However, with consistent practice, you'll get there, one small step at a time.
And, as with the old path, pay no attention to old habits. If you stop taking actions consistent with those habits, in time your brain will find ways of making the old habit pathways less active.
The key is practice. Do the work, day after day.