If creating good, effective habits is the way towards achieving what we want in life, how come everyone just doesn't pick a habit they want to form and just do it? The main reason is because sticking to an action long enough for it to become a habit isn't all that easy. A lot of will power and reminders are usually involved and as a result, we end up starting over and over again.
So here's what you do. Take an existing habit that you've already formed and attach a new habit to it. For example, you can use your habit of taking a shower at night to attach it to a new habit of doing push ups for example. The existing habit will already be triggered, once that happens, start the new habit that you want to create. This can be done before or after the existing habit.
The reason why this works is because one of the hardest things about forming a new habit is triggering it to occur. Since you have to constantly remind yourself to do what you need to do until it becomes an actual habit, it's easy to forget. By using an existing habit, the trigger is already there.
A habit is just a set of actions that play out once a trigger occurs. With this habit linking method, all you're doing is adding on more actions. So with the example with showering and working out, the habit is no longer just showering, it's working out and then showering.
Try it out for yourself. Choose an existing habit and attach it to a new one.