on one's feet

Short definition from Wiktionary

Prepositional phrase

1. 1
   While standing up or walking, running, etc.
2. 2
   Able to stand; hence, healthy, well, especially after some previous illness.
3. 3
   In a satisfactory (non-physical) condition; happy financially, emotionally, etc.
4. 4
   Used other than figuratively or idiomatically: see on, feet.