Treadmill is easier.
.
I think it is 80% of mental problem. I know, I did it too, and more then once
Try this: instead of 8 min run do 5 min. You already can do it and you know that you can do this.
At the end of 5 min run make a decision jog 30 sec more. At the end of 30 sec force yourself for more 30 sec.
See how far you can push yourself
Do not look at the timer, listen music, think about anything else but finishing...
And it is very important to remember: It is OK to walk to complete the run. Do not feel upset about it!