tink, tink tink... where is my lifeline

Sunday night caught me tinking my shawl.. 574 stitches for 2 rows back down to a knit only row that I could see the stitches easily (not the best thing to do with black yarn). I have since added a lifeline to my knitting, which is the light colored yarn running through all of my stitches. That way if I make a mistake, I can frog back to that and the thread will catch all stitches, even the yarn overs and decreases in lace.... why didn't I know about this sooner (LOL)