Camarón que se duerme, se lo lleva la corriente.

“The shrimp that falls asleep gets carried off by the current.”

Complacency or inattention lets opportunity or danger overtake you.

No hay mal que por bien no venga.

“There is no bad from which good does not come.”

Even misfortune eventually brings some hidden benefit.

Árbol que nace torcido, jamás su tronco endereza.

“A tree that grows crooked never straightens its trunk.”

Deeply ingrained character or habits are very hard to change.

A caballo regalado no se le mira el diente.

“Don't look a gift horse in the mouth.”

Do not criticize or judge something given to you for free.

Más vale tarde que nunca.

“Better late than never.”

Doing something after a delay is preferable to never doing it at all.

Perro que ladra no muerde.

“A dog that barks does not bite.”

Loud threats often come from those least likely to act on them.