One thing I was ought by my father, who's learned me alot of chords, rythms and picking-patterns, is to do it waaaaaaaaaaaaaaaayyyy slow. Doing it fast is more likely to confuse you and pick the wrong string. Try slowing iot cown completely, even if it's rediculously slow, to a pace you can easily play. You are much less likely to fail since you give yourself more time to react and pick the proper string. If you are able to pick it in the proper order loop it and play it steadily faster. and faster. Eventually it will be easy for you. That's just my 2 cents