No matter how experienced a knitter you may be, or how carefully you follow the pattern, there are always times when you make mistakes, and have to correct them.  Sometimes it just involves a simple correction, unknitting a few stitches or dropping a stitch down a column to fix it.  But sometimes the only solution is to pull your needles out, and rip back an inch, or two, or three, or ......... *?!/#!+#!  The most intimidating part can be trying to get all of those pesky little stitches BACK on the needles after you've ripped back past your mistake.  It is much easier to pick up those little loops if done with a needle (a circular needle works best) several sizes smaller than the one you've been knitting with.  That way, the needle slips easily through the stitch loops without disturbing them and possibly causing them to drop down a few more rows.  When you knit the next row, you can put the correct size needle in your right hand, and simply knit the stitches from the smaller needle back onto your project needle.  It doesn't make up for the time you will spend reknitting your project, but it does make the process a little less painful!