Why can't I get high!?

Okay so I heard from almost all my friends that you can't get high the first time you smoke weed, so me and my friend smoked for the fist time and they were right nothing happend to either of us even though we took like 6 or 7 hits each. But then her and I smoked again for the second time yesterday and and we both took like 3 hits, she got high and I didn't? I don't understand and it's not fair. I know that I AM inhaling and everything right, so I don't get why i can't get high?