A sluggish run with a great ending

During my four miles today, my body felt sluggish, and I took frequent walking breaks during the run. However, I ran the last half mile with a faster pace, but I could tell that pace was faster than my body could handle, because I had a hard time maintaining it during the half mile. My average pace for the half mile was measured as 10:08. Now, if I could maintain that pace for 3.1 miles I'd be ready for the race on the 21st.