APAD:Once bitten, twice shy.

Once bitten, twice shy

This proverb means that after a negative experience, people may be more cautious or hesitant to try again. Just as being bitten by a dog might make someone wary of dogs in general, a bad experience in any area of life can make people more hesitant or cautious in the future. If you've been hurt or had something go wrong the first time, you will be fearful or careful about doing it again. This phrase is commonly used to express the idea that past failures or negative experiences lead to future reluctance.  

The literal interpretation of this phrase likely originates from the experience of being bitten by an animal, which makes a person wary of going near that same animal (or any similar animal) in the future. 

Figuratively, the idiom applies to any situation where a person has had an unpleasant experience, like a failed business venture, a bad relationship, or a time when they were let down by someone. 

Example: 
Someone who was promised repayment on a loan but never got their money back might say, "I'm not lending him any more money—once bitten, twice shy".