If you pass all the requirements to become a full fledged navy seal, can you just quit on the spot?

Though, NSW/NSO jobs are volunteered (I call it, "the second volunteer"), you have to sign the contract stating that you "volunteered" for that duty. If you have earned yourself a Trident, you cannot just quit. You can try refusing to follow orders, but you will be charged with violating UCMJ (I don't know which article, but I'm sure the Navy can come up with few charges against you).