Bread's crap (in general, unless maybe whole grain bread), bananas are also crap (for pre-training, they're much better post-workout).
Have some lean meat with some "slow carbs" like rice or pasta 1-2 hours prior to training.
For the original poster, try to do shorter periods when practicing them. Like, do them for 5 mins, then move on to something else, then return to HTWs. You can try with HIIT for building up you anaerobic and aerobic capacity, but better just stick to FS, not sure how much carryover would it actually have.