How to forgive yourself for a stupid choice and just move on?

Basically I think I'm about to fail a drug test for a really great internship that wouldve paid $22 an hour and it would have been a great stepping stone towards my career. I did not want to do anything to fake the test except exercise and fluids. I took a home test for THC right before I had to go to the lab and the home test was positive. So I am pretty sure I'm gonna fail. I quit about 3 weeks before the test, when I found out I had to take it. I am so devastated that something like a little bit of pot is ruining this opportunity for me. I've been crying, barely sleeping at all, and I am literally sick to my stomach because I am so upset at myself. I feel so depressed. I am trying to accept it and move on with my life but all day and all night I am just filled with hatred for myself and my stupidity. I am so angry and upset with myself. Im having a hard time getting out of bed, and Im so nauseous and stressed out I can hardly eat. I keep trying to tell myself I am a good person, I have a 3.7 gpa in college and I work so hard in school, and this failed UA is not gonna prevent me from finding a career... but i cant get the guilt and anger out of my mind. WHEN WILL THIS GUILT GO AWAY!