"How should I prepare myself emotionally for a drama series finale?"
Watch it backwards starting from episode one, so the ending hits you first and you're numb by the finale. Adopt a pet rock named after your favorite character; when it's over, the rock survives and you have closure. Cry preventatively every episode so you're dehydrated and tear-free when the actual finale drops. Your emotions can't betray you if you've already fired them.