How do you trust again when you have been robbed?

I took in my granddaughte's boyfriend, we treated him like a son, I cooked, cleaned and did is washing etc. Then a couple of days ago I went on line to check my bank account and it had only �1.18 pence in. It had all been drawn out. He had taken my bank card, got my pin number and took all I had. He has now been arreseted as he was on the CCTV and we identified it was him. My granddaughter is heartbroken and myself and husband are devistated. He even told me not to worry as he would be giving me his board at the weekend. He even sat there when the police first came and never flinched or looked worried. I am gutted.