How can one avoid the suffering after getting cheated?

Today I suffered severe disappointment because I thought I was cheated some amount of money. I couldn't complain to anyone because I had no proof. And I suspect those who cheated me will also cheat other people. I want to avoid such disappointments in future and also I want to do the right thing. What should be my response on getting cheated ? Should I forgive the thugs who stole my money ? Should I wish bad for them and report it to the police or the managers?