Here’s an example: you choose an apple which tastes delicious. You assume you are very skilled at choosing apples (when in fact the whole batch happens to be good today).
Another: you enter the lottery and win millions. You assume that this is (partly) a result of how good your lucky numbers are (in fact lotteries are totally random so you can’t influence them with the numbers you choose. Although most of us know and accept this, we still harbour an inkling that maybe it does matter which numbers we choose).