Worst DIY mistakes you've made?

[Blue Coder]

Attempted to drill into brick with the wrong drill bit. Barely made progress and burned through the bit.

Tools matter more than expected.

[Diane82]

Thought eyeballing spacing would be fine for multiple hooks. They are all slightly uneven.

Close enough... but not really.

[HangmanPage_WCW]

Used the wrong type of paint for a surface. It never fully set properly.

Sticky regret every time it was touched.