Walking is good for heart health and diabetes control as long as you do it safely and with adequate precautions. Overdoing can cause more harm than good since you are a heart patient and a diabetic on insulin. Get your eyes checked by a competent eye specialist as diabetes increases risk for retinopathy or diabetic eye disease. Walk only as much as your body allows you to do comfortably. If you get cramps, heaviness in chest or legs and shortness of breath, report it to your treating doctor and do not continue walking beyond your comfort levels. If you can comfortably walk for 15 minutes a day, then walk only for 15 minutes but be regular. That is more important than walking for long distances but irregularly. Carry some sugar or glucose, sweets or candies/fruit juice when you are out for a walk, as diabetics on insulin are prone to hypoglycemia or low blood sugar. If you feel dizziness, sweating, confusion or trembling, consume 15 gm of glucose or sugar to prevent hypoglycemia. Stay active throughout the day and control your diet for managing diabetes and heart disease.