A lot of things have end dates and deadlines.
But with health and fitness, there is no finish line.
When you give yourself a finish line, and a strict deadline to reach your goals, you are going to be bummed out and disappointed when you don't reach them in a certain amount of time.
You shouldn't be viewing health and fitness as this thing that you pick up for a few weeks and then put it back in the closet to collect dust.
Health and fitness is a lifelong journey, and it's a lifestyle change.
When you view it like that, you are going to be more kind and forgiving to yourself going forward.