I'm just starting Week 5, so I'm no expert, but I've noticed a few things help me with regards to hitting that wall...
1) Pace: Holding back a bit on those initial run portions and going all out in that final minute keeps me from tiring out early and helps me look forward to that final minute when I get to let go.
2) Rest: Sometimes a run is particularly hard and it helps to have that day in between to recover both physically and mentally.
3) Heat: I find it a bit easier to run later in the evening when it's cooler.
5) Shin Splints: While sitting with your feet off the ground in front of you, trace the alphabet in the air, moving only at your ankles. Super easy to do throughout the day, at the desk, while watching TV, etc.
Hope some of that works for you too! Best of luck!