Traditionally, I've been a huge advocate of earning your rewards. I don't believe in eating chocolate or shopping something you desire or taking a holiday without working your butt off beforehand. For some people, getting the reward first makes them feel obligated to work overtime afterwards to deserve it, and that motivates them more than the first option, but whichever way you like to see it, the reward is earned by working overtime. This brings us to today's topic: if you should live your life in short sprints, after which you reward yourself with something nice and motivating, or if you should have a monotonous lifestyle that has little to no rewards.
For example, at the moment, I'm executing a straining challenge that started a week or so ago and will continue until the end of May. During the challenge I eat in a specific way, exercise in a specific way, get certain projects done, and work on other projects regularly. I tend to have these challenges several times throughout the year and make them overly tedious. To motivate myself to get everything done time, I've made a deal with myself that I get to purchase some organic beauty and cosmetic products if and only if I make it. (I didn't want the reward to be food and I've been out of mascara for years now.)
But here's the thing: if you live like this, or if you have challenges like these regularly, your subconscious starts to think you get to behave (eat, exercise, work) however badly you want after the challenge. For example, my challenge dictates I eat dairy-free carnivore until June, so naturally my subconscious is suggesting I start eating broccoli and oatmeal and celery and whatnot the second the challenge ends - and this, of course, will make me feel 100 times worse than I felt during the challenge.
So, in a way, you'd be punishing yourself for achieving your goals. And perhaps that's not a good idea. So what can you do?
Here's a possible solution: decide which tasks in your challenge are ones you'd like to, in an ideal world, do long term for maximum benefit, and stop treating those tasks as challenge tasks. Instead think of them as habits or a core part of your lifestyle. Treat certain singular tasks, like finishing a particular project, as the challenge tasks - and those tasks are the ones that will earn you the reward, not the lifestyle habits.
This way you might just get the best of both worlds: sustainable habits for your overall health and sprint challenges that take so short a time that your subconscious won't get used to them and that help strain your mental strength and earn those rewards. Perhaps you won't be able to do both simultaneously. But in time, you'll see just how much you're capable of.