Whether hurting ourselves or helping ourselves, both require effort. Consider the amount of energy that goes into a bar tab, how many hours of labor and stress precede it. That investment of time and energy gets poured directly into clouding and disorienting the mind, making ourselves less aware. Our faculty of decision making then becomes impaired, potentially leading to an even greater expenditure of energy in trying to sort out the further problems we've caused ourselves in that unclear state of mind.
There's a big difference between knowing what's good for us and doing what's good for us. The mind, too clever for its own good, often presents a myriad of reasons as to why we can't change for the better, and most commonly justifies stagnation through claiming that we don't have enough time or energy.
Certainly, changing habits is hard. The process requires a lot of time and energy, but so does remaining the same. So it's more a redistribution of the energy we're already investing. And as we see in the example above, in the long run, an unhealthy habit we refuse to change will actually consume more energy than it can ever give back.
Realizing that where we invest our energy matters, in regard to our own quality of living, and the quality of our relationship to others, we must expend our energy wisely. We make time to meditate daily in order to familiarize ourselves with the patterns of the mind, to witness firsthand which thoughts lead to unhealthy states of mind, and which lead to healthy states of mind. The practice also yields the skill, whether on the cushion or in the world, of being able to guide the mind away from these unhealthy thoughts, instead channeling it toward healthy thoughts.
This effort, when applied evenly, comes with an invaluable return on investment.