Don't worry about it EnragedPC - you gotta have something in ya that would warrant you to be in this training session that is coming up. Just suck it up and realize that you're capable of the pain! I remember back in the day when cross country required 7-8 miles a day for training, and this was during the heat of the summer w/ rolling hills everywhere... I never thought that I'd make it, but I did... and I know that if I'm capable of doing anything that is remotely difficult, then a football player like yourself would be able to do it too
"The pain is just weakness leaving the body"
Remember, no pain no gain... just think of how much more conditioned you would be after you go through these double sessions. Good luck =)