Considering how long it stays in your system.
Once I failed a drug test with a LOL - exceeds limits of lineraty but I was probably sober at the time.
One time after coming back from an adventure which was both positive and negative I was close to 200 but sober at the time. A week goes by (usually all I need is a week) without using and I dropped a little over 100 nanograms but still failed.
Point is you can register significant amounts of THC in your system and still be sober (hard to prove whether you are or not even if you are high). A high usually wears of in 45 minutes if you use occassionally but no more than 3 hours.
If I go years (I usually go at-least several months between use at-least) the beginning high scares the shit out of me but the medium and wear off isn't bad but then when I start using occasionally again I need more to even feel a high and it wears out pretty quick. Even weed in Washington was the color purple the high knocked me on my ass but wore off no longer than an hour and a half.