It's difficult to fix mistakes in a lacy pattern. That's why it's recommended that you periodically put in a lifeline. When you're at a point where you know your pattern is absolutely correct, run a piece of contrasting, thin yarn--some people use dental floss or embroidery thread--through all the stitches. Just thread a tapestry needle and slip it through the stitches as they're on the needle and knit as normal. The line will stay in there. If you make a mistake, you can rip out to the lifeline and know that you've got all your stitches on there. You just need to put them back on the needle.
Some people put in a lifeline after every pattern repeat, just to be sure. You can just slide the old one out when you don't need it anymore.