Yes practice helps!

I'm sorry to hear about your mistake and all the frogging, but I don't think any of us are strangers to this scenario and can certainly sympathize with you. I know how long it takes to grid. It is always best to grid when your alert and not fatigued. I always worry when I'm tired that I will make a mistake and just copy it all the way through every row and column ):

I have done frogging many times. Your problem is the reason I don't do gridding, because I don't want to find out I am off when it is too late. My marking my pattern works great for me and I have rarely had to frog more than a couple of stitches. Good luck with your project.

Oh, man! Not fun! I start in the middle, working up and out... Double counting the axis center vertical and center horizontal. It is so easy to get "off"! But visually checking often will usually keep you straight. You don't have to start over stitching. If you are using the red fishing line it pulls easily and is re-usable...Good luck.

A little experience goes a long way with this stuff and we've all been where you are! Just take a break, think it through, giggle, and continue! :)

I'm with Syagel regarding the gridding. I yellow highlight what I've done on my "work" pattern.
I''ve had to "fudge it" in a few of my patterns, but not more than 2 stitches and most the time it is after I've stitched so far into the pattern, that it is either "start again" on a new piece of fabric or pull ALL the work out (hours it would take to do that) and probably make a mess of the fabric. I'm NOT entering my patterns into any shows/competitions to win awards. I am willing to let anyone who wants to count my stitches one by one and compare it to the pattern, to be my guest..... :)