Last week I switched to running outside for week 7 - was doing 30 mins at 8kmh and was fine. Was treadmilling 20/25 mins at 8kmh no problem but for some reason since coming back on the treadmill just can't get through the late teens. I keep needing a minutes break - I'm pretty sure it's psychological but I am really struggling pushing through it. I want to stay on the treadmill because I get instant numbers (calories, distance, speed etc). Any ideas on how to get past that shitty 18th minute?