Hitting a Wall

It seems like every time I workout, or, more specifically, lift weights, I hit a wall. Nearly every single time. Why does this happen? Am I not eating enough? Am I eating enough, but not enough of the right things? I always have my Shot Bloks with me, and they are a life saver, but I don't think that I should rely on them all the time. I could keep this quote in mind:

Maybe it's Oli's fault for giving me workout plans that are too hard. Although it's not like I don't finish my workouts. I just about die 3-4 exercises before I'm done with the whole thing. Then I eat 2 or 3 Shot Bloks depending on how bad I feel and the carry on. It's not always bad, but it does seem like the past few times I've worked out I've crashed. Tonight my husband was very encouraging. Just 3 more sets; now just 2; last set boo-boo, you can do it! He's great (by the way, despite my wall hitting tendency, I did way better than him in our workout tonight!). To make you understand a little more about why I might be regularly hitting walls, below is a list of the exercises that we had to do tonight.
15 minutes on the elliptical at level 14
4 sets of walking lunges - roughly 24 each set
4 sets of hamstring curls - 15 per set, weights 30/40/40/30
4 sets of hip adductors and abductors - 15 per set, weights 40/50/60/70
4 sets of back extensions - 15 per set
4 sets of one leg calf raises - 15/12/12/15

And then, because we like to punish ourselves we did our burpees. I did 7 and DH did 10.
Now I'm tired because I've been up for almost 18 hours and because I kicked my own ass at the gym.

One other thing that I've done is tentatively agreed to run the Knoxville half marathon. I don't know when it is and that is the biggest determining factor for me because I have to have enough time to train for it to get ready, but I might be able to do the 5k that's associated with it if I don't do the half.

So, today's questions are these: What do you do when you hit a wall during your workout? and What do you recommend as your pre/post workout meal/snack to bring your energy level back up? Let me know in the comments below.

Oh - and a post script - have you ever made food in a jar to freeze? I've made lasagna and apple pie but I'd like to make something else. Do you have any recommendations for that?

R