maintain

verb5

1. •
   to keep something at the same level or in the same state, so that it does not get lower or weaker

   • It’s important to maintain good posture while sitting.
   • She struggled to maintain her composure under pressure.
2. •
   To keep in good condition and working order.
3. •
   To declare or affirm (a clause) to be true; to assert.

   • Pullman traditionalists will no doubt maintain that the full-service-at-every-seat principle is popular with their clientele; [...]. — 1962
4. •
   (slang) To keep composed; to keep one's head up; to stay confident, strong, self-assured; to avoid being a victim; to keep oneself from falling apart.

   • No matter what, you gotta maintain.
5. •
   (no longer used) To support (someone), to back up or assist (someone) in an action.