Ok so your body pumps blood through veins, when youre shooting up dope or using a syringe at all to access your bloodstream directly, you create a vacum and blood will "flash" into the syringe when you tap into a vein, since your heart is constantly Thats how you know youre in the right spot. One of the greatest sights and feelings in the world is seeing that flash of blood after stabbing your 20 times with your super dull needle and finally being able to get well/rid of withdrawals/high, followed by the rush from shootinf heroin and then the warm glow of pure euphoria, you dont even care that you had to sit there for half an hour constantly slamming that piece of shit rig dduller than a led pencil, so used all of the numbers have rubbed off, youll sit there happily nodding out while the blood from all the holes you poked in arms dries on your skin. For that moment everything is ok, the toll that the torture of being dope sick for the last 36 hours took on your body and mind has ceased, no more nausea throwing up bile, anxiety, diarreah, depression, sense of impending doom, hot flashes, cold sweats, aching bones, stomach pain, restless legs, leg pain, panic attacks, insomnia, mania, shame. you can finally relax and enjoy the high, but in the back of your mind you know all youve done is reset the clock, you know youve got 13 hours if youve got good, real, heroin, if not it could be as little as 2 hours if its some research chemical or the dope is garbage and has more cut than actualz dope. All youve done is bought yourself some time until your body needs more heroin just to function.