It took a bad failure for me to understand the importance of staying within FTP

I have been wanting to do this climb called Rist Canyon. It’s about 3000 ft of elevation gain in 12 miles or so.
The first time I tried, I pushed pretty hard at the 2000 ft elevation gained and sustained 300ish watts for 5-7 minutes.
By the time I had last few switchbacks left, my head was throbbing so bad and I couldn’t take another pedal forward. So I turned around.

Talked to my coach and he explained to me the importance of staying in FTP.
So, I promised myself to not get too excited and stayed within my FTP the following weekend. Didn’t whole 47 mile loop pretty well. No headache or crazy cramps afterwards either.

First chart is the successful attempt in the second weekend and the next chart is the failed attempt.