Going to the gym to get fit? Sorry, you've got it all backwards.

(And that's why you'll quit after a while—as you already know.)

Mistake 1: Trying to lose fat by exercising

Do you suffer from stubborn fat you haven't been able to shift? Attempting to burn more calories won't help, if your hormones are telling your cells to hold on to fat. What will work is to rebalance your metabolism. To lose fat, nutrition beats exercise.

Mistake 2: Trying to build up muscle by drinking protein shakes

Protein is biologically necessary to build muscle, but not sufficient. To build muscle, we must primarily use muscle. Intensively. That's where exercise beats nutrition.

Mistake 3: Trying to get fit by going to the gym

That's where the most significant mental reframing is necessary. Going to the gym in order to get fit is hard to sustain long term if it's a chore—if it's the hard price to pay to look good and to increase your chances of reproductive success.

WRONG: exercise (while puffing and hating it) in order to be healthy

RIGHT: be healthy in order to continue to engage in the exercise you love

Me? I don't go to the dojo to get fit. I try to stay healthy (managing disease through nutrition etc) so that I will be able to continue to go to the dojo into my 80s and 90s.

From a whole-life perspective, exercise only really works when it is its own reward.