You should do what your teacher sais. He's afterall your teacher. Slow down, relax. First learn the paterns combined with the picking then gradulately start playing faster. Like so many wise men told before: 'You need to learn how to crawl before you can walk' It might sound like ****, but once you've got the fingering nailed I'm sure you'll get the picking done too. There is no 'easy' way to correct a mistake like that I think. You have memorised for 6 years to 'doublepick' the notes, well, it will take some time to unlearn in and do play it how it should be done. It depends on you how long it takes you learn it right. Besides, speed isn't everything, learn the patterns then speed it up. Owyeah, and you should use alternate picking ! You paid for a teacher well, you should listen to him :)