1. Assume that a character you love is going to dieJoss Whedon taught us this: when you start to love a character you should ALWAYS assume this means they're going to die suddenly. If you become emotionally invested in a TV show and forget this, then your heartbreak is your own fault (#sorrynotsorry). There are various theories floating around the internet and my money is on Mary (John's wife) dying in "His Last Vow". After reading this fantastic article on Den of Geek I'm even more convinced she's not going to make it out of series three alive.
Mary is new + fans love her + John loves her + Sherlock likes her + she's pregnant = dead in finale.
2. Join TumblrYou're going to need to talk about your feelings so get a head start on the finale and join Tumblr now. If you think that Tumblr is the place where the crazy fans live, then you're kind of right, but it's also full of detailed character analysis, beautiful wit and amazing GIFs. The BBC has been using Tumblr to promote the show and deserves a slow appreciate clap (80s movie style) for their content and approach. Give Tumblr a chance and you may find yourself entertained and consoled by your fellow fans.
3. Watch the hair ruffle GIFs again and again and againWatch the GIFs of Sherlock ruffling his hair before the final episode starts. I think this is the Sherlock equivalent of cute cats, because you're guaranteed to be in a happier place after watching. See below - don't you feel better? Repeat as necessary.
Good luck everyone! See you on the other side...