The university of life
Definition 1 of 1
Pro Tip 1/3Metaphorical Learning
It's a metaphor suggesting life experiences can educate like a university. 
She keeps learning from the university of life through her adventures.
Pro Tip 2/3Informal Usage
This phrase is informal and better suited for casual conversation. 
My brother's wisdom comes from the university of life, not a lecture hall.
Pro Tip 3/3Emotional Resilience
Often implies resilience gained through personal challenges. 
After coping with loss, she graduated from the university of life.