Push Up Challenge- Week 2 Down

I am beat, I am not going to lie this week got harder and harder for me.  Typically I was good for the first 2-3 sets and then the last 2 were a struggle.  No pain, no gain is what they(whoever "they" are) say.  

Week 2 Stats:
Day 1 14-14-10-10-15
Day 2 14-16-12-12-17
Day 3 16-17-9/5-14-15/5

I know you are wondering what those slashes are on Day 3.  That is me totally maxing out and saying "NO MAS!!"  Really, I kick myself but honestly I was exhausted.  I tried to mentally pump myself up but it worked on set 3 but not so much on set 5 when a minimum of 20 was required.  Errrr those slashes frustrate me because  I didn't push past the 17 I did in the last set on Day 2.  Motivation for week 3 I guess.  Maybe I am working out to hard before I do the push ups.  I like to be warm but perhaps I should just do 5 minutes of jumping jacks and jump rope before starting.  For the past two weeks I have been doing my full cardio (2-2.5 mi on the treadmill) before the push ups.  Next week I will try doing my push ups first and then cardio.