The phrase "sobering experience" means an event or situation that makes you serious or thoughtful, often by making you realize the seriousness or harsh reality of something. Full definition
Buschman, the owner and chief executive of Buschman Corp., a $ 3 - million manufacturer of parts for paper machinery, based in Cleveland, had an especially sobering experience early in the company's development: «We were in a position where we had a lot of cash, and I thought everything was going well. (inc.com)