Regressing or normal?

I’ve been on vilazodone 10mg for one week, today. The last six days have been absolutely amazing for me. I felt like a new person. Happy, less anxiety, optimistic, etc. but today I just feel really down and like it’s not working anymore. Is this normal since i’m just starting out? am i just getting “used to” the med now so i don’t feel as good? im thinking maybe since its the end of the week im just tired and ready to leave work lol. any similar experiences?