If you reward yourself before forming the habit to achieve your goals, you are doing it wrong. That is exactly like the old idiom ‘putting the cart before the horse’. Long term goals require everyday(or periodic) habits. Our brain is wired to do things only if there is any reward, at least to begin with, before the habit itself becomes a reward.
So, to train the brain to stick to a habit you need to reward it. But do not reward it too soon. For example, you want to get fit by cycling or running, and you buy a new INR 35,000 bicycle or INR 10,000 shoes before day 1 of starting the habit, you will not be able to form that habit because the brain knows that it already got the reward!
That is why cheat days are at the end of the week, tips are given at the end of service in an restaurant, bonus is given at the end of a quarter or year and so on. If you think that you will start cycling from tomorrow, but first you get that expensive cycle, it will not work. Do it in the right order and put the horse before the cart, where it belongs.
Note: Of course you need a bicycle or shoes to start those activities, see if you can borrow a bicycle from a friend (who failed their resolution last year). Shoes are best bought but first go for walks for a month before investing in those expensive shoes because now you already got into the habit of getting out for physical activity everyday.