A post workout shake is good for recovery...but a high protein diet is what you need overall. Grilled chicken, fish, eggs, etc.
I really tightened down when I started running my cardio in the middle of my heavy routine. I do six-seven stations on training days. I'll do the heaviest lifts first then 30-45 minutes of cardio, then the last three afterwards. I train a total of 4 days a week, but I only mix the cardio/heavy weight on 3 of those. Day 4 is a straight weight day. It sucks lifting after good hard cardio but if you can push through it works. Remember, working out is a mind game. You can do more than you think you can and it comes down to a decision not to quit.
And
at me recommending Crossfit originally in this thread. Don't get near that bull unless you want to get injured. I said that before I researched it closely and knew any better. I heard of several people I know blowing out knees and shoulders.