Lunch and Energy Question?

I was wondering today. I brought my lunch to work, but its one of those small lunch kits of tuna with some crackers , that has about 220 calories all togther. I dont think that will fill me up to satisfy me? Or should I just go grab a good ol' Subway lunch, like a 6inch turkey sandwich? Reason I ask, is beacuse yesturday for lunch all I had was a Campbells chicken noodle soup with a gl of OJ and an apple. I went to the gym and started my regular workout routine; 20 min cardio....situps and then I went to work on my chest. I was doing some flatbench presses. I usually start out with 25 on each side to warm up and then go up to 45's on each side. Well yesturday for some reason, I felt really weak when I started on the 25's????.....That was a really weird feeling and a big loss of confidence in myself. I only went up to 35's on each side,because i felt like I could not do anymore?..... I was thinking maybe I did not have a good lunch?....So therefore, I felt weak? Please help...