Drama with partings ( Every loc starters nightmare)

Guys, I'm stressing out about what size partings to start my locs with, I know  I shouldn't be because every locced persons parts are unique, but I can't help it. I'm scared that they'll start them off and I wont like the parts. But then I think I could start them myself but I'm really bad at making straight even parts. So gettting them done professionally ( whatever that means) Is the  best option for me. I know I want them medium sized but medium is not a generic thing. So thats what I worried about if i'm honest. I know noone can  predict what size they'll be when they finally mature but i'm just really nervous. because this is something I plan to have for the rest of my life, so I just want it to be atleast close to what I want them to be. But I guess I'll have to discuss all of this with my loctician, and see what they say. Pray for me guys, I just hope that this isnt going to be something that going to deter me from getting them or taking them do when I finally do. But I know sometimes when you want something so badly you just have to make sacrifices, and see the positives to every situation. So I know i'll be okay, even if my parts are wonky or to fat/ thin. I'll just have to work with it. I guess that is the beauty of locs.