You only get one body, mind, and spirit.  If you don't take care of them now- in the present- you are allowing your body, mind or spirit to deteriorate- to weaken.  Sure you can put off an oil change for your car as long as you want, but at some point your car will break down and you'll have to buy a new one.  You can't buy a new body.  You can't buy a new mind or spirit- and once those are broken they are almost impossible to fix or heal.  Don't let yourself get to that point.  Take care of your body and it will take care of you.  Invest in your health.  Invest in your future.