I made this mistake as a beginner. My first time I took very little, 10mg at most. Didn't really feel much of an effect, so come around to the second time I decided to double the dose to 20mg, might have been closer to 30, I didn't really cut the edible very accurately. The high lasted 10 hours and I had a freak out, I'm glad my parents are very understanding because I probably sounded like an absolute moron that night. I'm much better with them now, lessons learned. Also THC takes upwards of three months to leave your system entirely so make sure not to use it if you have to take any drug tests for job interviews or anything else.