Good luck. If you forgot about the amount of pain, you may have forgotten that the worst is about 2 weeks after. The pain causes you not to sleep, but the pain killers cause you to have bad sleep. The lack of quality sleep builds up. But since, you're doing the second one, you know that in the end it will be a lot better!
My wife just had her first knee replace 2 months ago. She if finally at that stage where she forgets about it, and is able to be normal again. One of the biggest things that helped with the pain and swelling was a Cold Therapy Machine.
Had 2 hips replaced and a knee , the knee was by far the worst . I slept in a recliner for 3 months with the knee . I heard the new way they are doing it now isn't quite so invasive , time will tell on that one . All of my replacements after some time turned out way worth it .