I Take Metoprolol Tartrate, 50 Mg In The Morning And

I take metoprolol tartrate, 50 mg in the morning and 50 mg in the evening. I am tired all day. Pulse runs about 55-57 during the day. 75 years old. Walk 1.5 miles each morning. I'm thinking tiredness caused by too much MT. How do I safely reduce dosage to 50 mg in the morning and 25 in the evening. Also taking 40 mg Lisi ipril and 6.25 mg HCTZ each morning. BP runs about 115/65