Just keep practicing. Size 4s (or 4mm) are pretty small unless you're using a very thin yarn and will make a very dense and tight knit with the worsted. If you can try using a size 9 or 10 needle and it may be easier to make the sts more even and not miss a stitch as the stitches will be larger and easier to see. I think that will help quite a lot.
sue- knitting heretic