Greece: got scammed - How to get over the feeling

Need to get this off my chest: I got, for the first time in my life, scammed.

Was driving on a remote road in the mountains, and saw a guy selling something along the road who tried to stop me. He told me about his work on the farm and about the goods he was selling. So far so good. I asked him how much something cost, but he said: I'll make a good price for you (this is the red flag I should have noticed and acted on). Then he kept talking and adding stuff and when it got to payment, the price was surorisingly high but I was assured it was because of the quality of the goods. When paying him he did not return my change (which was like 20% of the price) and just gave me a bit of extra product - where half of the products in the end seem to be rotten when I got back to the hotel to taste them.... Lost €70 and feel incredibly stupid. It really ruined my day and it's really hard to not think about it...

Any advice on how to think about this to not feel bad about it all the time as it's ruining the rest of the vacation for me? Thanks!