I read Matthew Perry's memoir a couple weeks ago. It's about his addiction to alcohol and opiates. He went to rehab 10+ times. His withdrawal symptoms were worst on days 3 and 4.
Even after 14 surgeries from drug effects, he still broke his sobriety and sneaked opiates when cravings hit.
After reading the book, I realized I probably have a sugar addiction. If I don't eat sugar for a day, I experience intense cravings. For an hour, it is hard to focus on anything except eating a dessert. I thought it was emotional eating and a stress response and lack of willpower, but now I realize it is probably a physical addiction.
When cravings hit in the past, I thought they'd go on and on forever if I didn't give in. I always caved. Had I known they were temporary withdrawal symptoms that would gradually subside over a few weeks, perhaps I could've powered through!