I've been thinking about why it's so difficult for me to switch gears on various aspects of my life: diet, sexual expression, attitude towards other people.
I'm the kind of a guy who, knowing why he does something, would do it regardless of circumstances. Since dropping soda from my foods list, I haven't had a drop of the carbonated drink, even though I've skirted the definition a bit by imbibing energy drinks during the intense exam season. I adhere to the oath strictly, though I recognize that I came close to breaking it with the energy drinks, because I know it's good for me: ever since dropping it, I've lost some weight - not much, but noticable.
Which isn't to say that returning to carbonated drinks hasn't been tempting. For the first couple of weeks, I kept looking at the rows of bottles at the supermarket with the eye more intense than simple observation of environment. Recently, I was thinking about reward system for conquering physical workout goals: Coca-Cola, one I liked the most out of them all and one directly associated with running for me, was among the potential rewards for a few seconds before I realized I won't do it.
It was tempting for a while, but for some reason, I stuck to the rule. It was a firm thought through the whole thing: I don't drink soda. I have a theory on why it was, and why haven't I just turned back to it, especially during stressful times.
When you prioritize your own leasure - the way so many young people do nowadays - you adhere to a set of values that puts your leasure and comfort above everything. When the choice stands between getting a job and keeping playing videogames, the one with obviously more connection with your values wins. When it stands between working out or sitting your butt off all day, you know what you're going for in that sort of a mindset. It's about what you value most because it brings you most satisfaction.
Arnold Schwarzenegger's Total Recall was mostly a bland, white-washed recount of the celebrity's life, one thing stuck with me through it. At one point, Arnold had quit bodybuilding after winning many awards. He stopped prioritizing his body's attractive appearance that drove him through his bodybuilding career from the very beginning. Then, he was persuaded to compete once more, well after quitting for good. Having agreed, Arnold made himself recall the mentality of his body being priority once again. He said he had to persuade himself again that the muscle growth was important again, because at that point, he was already thinking about something else (probably his growing business).
In other words, he had to move from one set of values - whatever it was - to another, that of bodybuilding and competition.
Life changes aren't just about you setting a new list of rules for yourself: like choosing a new master, there must be reasons you'd want to follow the different path, lest you're bound to return to the old ways: they, at least, still have the value of familiarity. What you choose to move towards must matter to you, lest you snap back when you can't find it in yourself to remain at the new spot.
My guess is - people fail changing their lives, especially in radical ways, because they're still hanging onto old values while trying to apply new ones. The idea of the workout sounds good, but the workout itself might seem dreadful if you haven't done physical for a long time. The only reason you'd stick to it is either survival instinct kicking you to or other, similarly strong adherence to the principle behind it: gaining physical strength, endurance and confidence through capability.
That cake seems tempting because you're still considering the pleasure of its taste more important than what it does to your body and mind. That mile a day seems like a hellish and completely unnecessary overworking of your body because not only do you not see the benefit of physical conditioning (which is why you're in this position in the first place) but also don't consider the benefit of discipline and the fruits the brings. That book seems like a waste of time when you can spend it better pushing your in-game resources to the max and unlocking 100% of everything.
Taking up new values takes time and consistent effort. You can't make up your mind about it and act as if it'll set up on its own. It might seem that it does because your environment already encourages you into that direction - a valuable influence, but even that not always enough. You can't rush a thing as conservative as your mind's core values: you will only make it snap back. Defense mechanisms of such a complicated machine are not to be ignored - or trifled with.
Steadfast regularity can a long way. Find a healthy diet and exercise routine that is sustainable, and stick to it.
You can do it!