7pm is the new midnight in my world!

Why is it that I am completely useless after 7pm? Here I am trying to work on my routines and such and then 7pm hits and I am not wanting to do a thing?? I am so tired from the day and I think I have hit my coffee consumption max so even if I had a caffeine IV drip, nothing would seem to get me going to get stuff done! What do you guys do in the evening to keep going?