willsmadnan,
I have a good hairdresser, but... I have watched manuals on U tube and can cut my own fringe with confidence in between visits to the hairdresser (doesn't the fringe always grow too fast ! ) and sometimes have been known to 'feather in' other parts. I also dye my own hair and experiment with 'shading'...LOL
Sometimes I get it right and at other times I don't... she always knows when I have been handy with the scissors though, but in fairness to me - compliments me when I have done it right !
Like you though, I think I 'know' my own hair, and my own limitations, but I also know when I have exceeded those limitations.. which are in fact sadly for me... limited ..ha ha !