A couple that will encourage hardening up:
Lone Survivor, Marcus Luttrell - (True Story) 4 person US Navy SEAL team on deep recon in Afghanistan, engaged by Taliban, 3 of them shot multiple times - still fighting, eventually killed. 4th guy - broken back, broken shoulder, broken nose, grenade shrapel in legs, shot through thigh, no equipment except gun manages to get out. He also runs through a fair bit of their training. Very intense.
Warrior Training, Keith Fennell - Lots of detail about SASR training. He talks of a 30 minute 300 pullup, 300 pushup set they used to do.
SAS Sniper, Rob Maylor - Former Royal Marine Commando, then SASR Sniper. Also some very intense training. Then goes into a fair bit of detail about several missions in Afghanistan. He was also in the Blackhawk that went down on the HMAS Kanimbla in 2006.
While I in no way intend to join up, I am motivated to train a fair bit harder after reading these. What these guys put their body's through is amazing.