Learn English – Word for someone who is “pretentious”, but without negative connotation

Mentor or Motivator would work as alternative terms. (I like catalyst too)

Enabler picked up its negative connotation from psychologists. In relation to behavioral psychology it refers to someone who assists a person with self-destructive behavior - not just drug use, but addictions or negative behavior patterns of any kind. (Making excuses, assisting in covering it up, obtaining materials, etc). It's not technically a specifically negative term but at least in the US it's almost never used outside of the context of enabling addictions or other negative life patterns.

A person with a “positive outlook” could be described as a positive person. You could say he has a positive personality.

A positive person will hope to receive the promotion, but if he doesn’t he won’t be disappointed.

From dictionary.com:

positive
9. emphasizing what is laudable, hopeful, or to the good; constructive: a positive attitude toward the future; positive things to say about a painting.
10. not speculative or theoretical; practical: a positive approach to the problem.