There are very few valuable resources that only accumulate.
Experience is one.
Paradoxically: the bigger the loss, the bigger the lesson.
It should be relatively simple to identify when we aren't accumulating net new experience, but in practice, it doesn't seem to be.
This quote by Stephen Covey describes how we often trick ourselves by thinking of experience as something we endure vs. something we expose ourselves to:
“Some people say they have 20 years experience, when in reality, they have 1 year's experience repeated 20 times."