<p>I remember reading somewhere on CC about a boy who declined Harvard’s acceptance and went to his flagship state school for a presidential scholarship, but regretted the decision two or three days after May 1st and called Harvard’s admissions office. (if you search around you could probably find it.) It took a bit of paperwork, but they let him back in a week or so later, so you should be fine and they should take you back if you call up the admissions office and explain! The kid did not EVER regret his choice after that. If you really feel like Stanford is better for you, then go for it! Better go for it than spend the next four years regretting your decision and suffering from the workload. Good luck! :)</p>