I do counted cross stitch, and when I start to get tired I just put it down for a while. That is why it took me years to finish some of the ones I did for the kids rooms. Don't worry it you mess up as long as you can still tell what it is. Cause I can tell you that I have never finished one that was totaly right. The key is to do a little at a time, and take a break so your eyes don't cross. I always put a mark on the picture so I know where I am when I stop. I hope this helps.

Huge Hugs Louise