When you're old and curmudgeonly like I am you become set in your ways. It's hard to believe but some of these ways are wrong. Your habits are a result of your old thinking and most importantly your old actions. Since I know everything now, it's conceivable to me that a younger version of me may have made an error in thinking and ended up habitually doing something silly, without thinking, like screwing around with my iPhone at every single spare moment throughout the day.
See what I did there with the bold.
We do things, we make decisions and choices without even considering the options. Our subconscious not only can provide us with important facts, like all the words to the closing song of Gilligan's Island, it also will bring up complex thoughts like the results of thinking or provide a course of action. Don't believe me? Think of the last time you drove a car somewhere and had one of those realizations like, "Holy crap I'm driving a car and not paying attention to where I am or where I'm going! How did I make it this far?"
Learning anything requires repetition, so does unlearning. But before you start training yourself what you want to do, like Zippity the Zebra in Man vs. Beast you have to "realize it's a race." The key there is to set yourself a standing order to notice when you do some physical thing . Go on, put that subconscious to work for you noticing you taking the phone out, or eating that 28th cookie.
Now you are at that crossroads, where you make the choice. The thing you've done at up until this point over the last 87 times this choice came up, the thing you decided you wanted to change for some reason, will seem very compelling. It may even seem crazy that you ever wanted to or could change. Here is where you will need to have thought out the good reasons for why you will change, to overrule the habit and emotional response that is tied into taking that habitual action. What you want to do here is put yourself in the right frame of mind to realize, that, yes there are actually other things you might want to do besides restock the floors in Tiny Tower.
The way I recently learned and am trying to do that is to have a nice little slogan, "WWID?" This means, "What Would I Do? Where I, is me heroically taking into account my full hierarchy of values." This is a pretty general mindset, depending on the particular habit I'm trying to change I may just focus in on that one for a few weeks and have a different slogan to recall in my time of need.
So in summary, I plan to take certain things I don't want to do anymore and notice when I'm doing them so I can wake myself up enough to know, "it's time to make a choice," and then put myself in a heroic frame of mind to make that choice.