Sarcasm Stinks!

I have had 2 people in the last week be sarcastic to me in situations where either I was too overwhelmed to help the person (and their response was sarcasm) or I asked someone for help, and their response was sarcastic and accusatory too.

I hate it when folks get sarcastic. I don't know how to deal with it very well. I don't reply sarcastically, I don't think that would help. I just don't know what to do! I feel so defeated when people get this way with me.