I'm taking 25 mg Toprol XL once daily following a mild heart atta...

I'm taking 25 mg Toprol XL once daily following a mild heart attack in June 2008. What I have experienced is just an overall feeling of aging--tired, muscle aches, fuzzy thinking, forgetfulness, short fuse. I have very little motivation to do things around the house and tire easily. I accepted an invitation to golf this week, but I already told the group that I may only be able to do 9 holes. I don't feel like I could do 18. That's just not me! I have cut back to 12.5 mg. but still feel like a really old man. I complained to my cardiologist, but he said that my dose is too low to cause these problems. I am going to slowly reduce my dosage to 6.25 mg. to see if that helps. I feel my quality of life has suffered for taking this drug.