Yeah it happens, one post you get 800 the other 9 posts might get you 0.05$. Still it's 80$ per post ("the bottom line").
If you had a shop, generating revenue on daily sales (one day is a bust, the other day is good, the next 3 days are a bust, etc etc) this is more or less how you'd be thinking about it: https://steemit.com/steemit/@alexgr/dealing-with-variance-in-commerce-and-steemit-the-merchant-approach
It helps eliminate thoughts like "damn, 0.1$? fuck that". You put things into perspective by averaging the rewards.
This is certainly true. Managing disappointment can be difficult. This is a good way to maintain perspective.