The sky’s the limit
Definition 1 of 1
Pro Tip 1/3Metaphoric Sense
The phrase is a metaphor suggesting unlimited potential, like the vastness of the sky. 
If you keep improving, the sky’s the limit for your gaming skills.
Pro Tip 2/3Positivity Implied
The phrase is often used to express optimism about future potential. 
You've aced your exams, the sky's the limit now!
Pro Tip 3/3Colloquial Usage
Common in casual conversation, but may be too informal for serious or academic writing. 
Starting your own business? The sky's the limit!