How Can I?

I know somebody. This somebody has in the past done something bad. This somebody promised me it was not going to happen again, I could trust this person. This somebody broke that trust once again, but tried to minimize it by explaining they had not done ALL that they had done before, just a portion of it.
How can I trust this person? This person has shattered my trust over and over, and I am in little pieces right now. I can't do this! I can't keep going through this over and over.
I KNEW something was up, something in the back of my mind said so, but I ignored it, put it aside as paranoia and blamed myself for doubting...and my little voice was right! I am so disappointed and hurt and angry and shattered and shaking....I can TOTALLY understand what can drive people to drink, to try to drown their sorrows. I, however, haven't got the money to try.
So much for climbing out of my depressive slump. I give up.