Today when I was exercising…?

So today when I was doing my usual exercise routine, I normally jog/run 4 miles daily and do a cardio-ab circuit video.. I got through the video and 2 miles and my legs started to get really sore to the point where I had to stop. How can I make up those 2 miles in other easier ways? I’m going to a fair tonight… so I’ll be doing a lot of walking. Or should I run 2 extra tomorrow? I am trying to lose about 5-8 pounds.