Make a list right now of things that need to be taken care of, and assign dates to them. That way you don't have it all bubbling around in your head and making you anxious you'll forget something.

Most things have a natural time they need to be done by, and some things have a natural order of operations. Like, don't give notice at your job and your house until you are sure you are leaving, that sort of thing. Checking your gear can happen early so you have time to get repairs/replacements. You probably want to hold on to the cat and the mail a little longer. (Really, you're giving up your cat? Awwww)

Everyone has a different set of things, depends on if you are renting or own, subletting or moving out, what your bills are, how long you're going to be gone for, what you're doing about your job/school, what gear you have & what you need to acquire, etc.

What do you mean "if things don't pan out?"