A little gall spoils much honey.
More Portuguese Proverbs:
A little knowledge is a dangerous thing.Portuguese
Your windmill dwindles into a nutcrack.
Portuguese
If you would make an enemy, lend a man money, and ask for it back again.
Portuguese
A pig on credit makes a good winter and a bad spring.
Portuguese
A looker on sees more of the game than a player.
Portuguese
Rather a husband with one eye than with one son.
Portuguese