How long do they persist? 1 day, 1 week, a year, ten years? I used to be a daily smoker and was horribly addicted. Now, at least ten years after I quit, I find myself having trouble remembering things. I lose my train of thought a lot too, really annoying. I don't know if that was attributed to my cannabis use, or just my brain in general.
That said, my friend, 10 years of life make you forgetful sometimes.
That's just called living.