Executing Saturdays 10K Race Plan

I am working Evenings this week, last night at 11pm I jumped on the treadmill to give my race plan a try. Did the first 4K at a 4:30 pace , I really felt like I was cruising the breathing was good and the effort was easy. AT 4K I ramped it up to a 4:15 pace , I held this for 3K. it wasn't too bad but I was breathing heavier and there were moments of I am not sure I can keep this pace but I kept pushing. At 7K I ramped it up to a 4:00 pace, this was definitely pushing the 02 Max and the HR was pegged but again I had more moments of you cant do this followed by brief intervals of its alright. The last 500m I picked it up to 15.5 kmh then 16.0 kmh then crossed the line with 42:38 on the clock. This is the fastest I have ever run 10K , a few times before I broke 44:00 on the treadmill and my race pb is 44:51. Its a given that I will break 45:00, how close I get to 42:XX I am not sure.