General Antonyms:
* Realistic
* Practical
* Pragmatic
* Down-to-earth
* Sensible
* Rational
* Logical
* Level-headed
* Hard-headed
* Cynical
Specific Antonyms:
* Worldly (in the sense of being experienced and knowing the realities of life)
* Calculating (in the sense of being strategic and self-interested)
* Opportunistic (in the sense of taking advantage of situations for personal gain)
Note: The best antonym for "quixotic" depends on the specific context.