I would talk with your doctor; maybe he/she can lower the dosage that you're on. Everyone responds differently to medication, but some folks (myself included) are more sensitive to beta blockers and need a lower dose. Also, some people do better energy-wise if they take their beta blocker at night instead of in the morning.
Good luck.
Follow this link to side effects of the beta Blocker:
http://www.medhelp.org/drugs/Toprol-XL/show/218