Question on improving 1.5 mile time.

I run every day of the week with maybe one day of a fast paced run (which is usually 1.5 mile)

During the days where I train my endurance I run 6~ miles roughly and I just run at a comfortable pace, but the main issue here I want to blast my previous 1.5 mile time.

My previous 1.5 mile time was like 13:00 which was taken 3 months ago~

My biggest obstacle I think is probably mental...when starting the 1.5mile do you just give it your all and just breathe normally?

I remember back when I was running a quick mile my breathing became a pretty big issue but this was only when I was running sub 7mins or close to it.

Any help is appreciated it :]