When people say, "You're too intense about your fitness walking," take it as a compliment. You need to measure your intensity.
The recommendation for a walking exercise "training heart rate" is 60 to 80 percent of the fastest your heart can beat in a minute. Figure your maximum heart rate by subtracting your age in years from 220. Multiply the result by 0.6 and 0.8 to get the bottom and top of your target zone for aerobic training through walking for exercise. You can also check how long it takes you to walk a mile, then check again periodically to see your improvement.