Fumble
Etymology
From the literal fumble (to drop the ball, especially in American football). The slang widened via "fumbled the bag" (lost a lucrative or valuable opportunity), an AAVE and hip-hop phrase, and now applies especially to romance.
verb · /FUM-bul/
To blow a valuable opportunity through your own mistake, especially a promising romantic one.
What it names
It names losing something good that was yours to keep — not bad luck, but self-inflicted waste. It puts the blame squarely on the person who dropped it.
Example
He had someone wonderful and ghosted her over nothing — total fumble.
Related idea
The opposite of "securing the bag" (locking in the win); to fumble is to have it and lose it through your own error.