…Treat every success in your fiction like it’s a clue.  In other words, hide the holy shit out of it.  Hide it in plain sight.  Break away the second before the character succeeds, and show them after a time jump, struggling on the next thing.  Show the bad guys flipping every success on its head.  Lie.  Bury the success in a list.  Have the other characters mock the success.

In the end, the character has to have done a lot of things right.  But don’t let the reader know that.  “That guy,” they should be saying, “he just can’t get a break.”