I've never heard Calvinism talk about either "fortune" or the "prepared mind". I get that you're denigrating Calvinism here rather than making a precise statement, but what part of Calvinism are you referring to? The Calvinists I know would be more likely to say that God willed your situation or gave you the preparation for your mind. This is more akin to fate than fortune. ("Fate" being what will inevitably happen, and "fortune" being chance events.)
If you work hard and sacrifice you will be rewarded. Frequently it is presented as quid pro quo.
At the end of the day if you work hard and do well, you could still have been lucky. Rather than that negating all of your hard work, a better reaction to this fact is a bit of charity for others. And I’m not talking donations, I’m talking about being a decent person and not judging others who haven’t got what you got.