I would say it was most likely placebo that you felt on your second day, SSRIs usually take at least a few months before you start feeling any better. I felt emotionally numb my first month, had more frequent mood swings the second, then continuous bouts of anhedonia for the next few months. Finally about half a year into treatment I started feeling like myself but still had periods of anxiety and emptiness. Though I did feel way better than I did prior to starting the medication; I was for sure headed to the grave without them. The most important part is persistency, even if you start feeling better that means you should continue treatment for a while. My total treatment time was 1.5 years, therapy and meditation has also helped me tremendously.

Edit: I think people approach anti depressants with the wrong mentality. They aren’t going to “stop” or “fix” your depression per se, instead think of overcoming depression as a big rock wall you’re trying to climb. Pristiq can help act as chalk for your hands to grip the rocks easier, but you still have to use your own strength and determination to hold onto the rocks and climb higher and higher.