if our brains know that we are unfit, why don’t they force you to do exercise?

Question: if our brains know that we are unfit, why don't they force you to do exercise?
- Keywords:
  brain,
  exercise,
  unfit
Asked by anon-174244 to Yewande on 12 Jun 2018.
- Yewande Oyekenu answered on 12 Jun 2018:
  
  Our brains tell us what is wrong and what decisions to make. But being unfit is a subjective feeling, so we should exercise as a routine lifestyle not because of what we think our mind is telling us.

Question: if our brains know that we are unfit, why don't they force you to do exercise?