The way you've phrased your question leads me to think you're interested in hearing stories involving the death of a best friend, as opposed to 'loss' in a general sense. If it's all the same, I would like to share the story of how I lost my best friend, although I should point out that she is very much alive.
My best friend and I were together for 6 years. We shared our lives entirely, and kept no secrets. I was at my best and my worst when I was with her, and hid nothing from her. I look back and feel an intense shame sometimes as I recall some of the experiences we shared. There are times when it's hard to believe we're no longer together. There are times when I simply cannot understand my place in this world without her.
If you're feeling the same sort of sensation - a cold, hollow emptiness, perhaps - know that you are not alone. I don't mean to pry, but I can't help but think you've posted this thread because you have lost your best friend and want to commiserate with kindred souls, or seek out advice from those who have walked a similar path.
To directly answer your question though, my life has been good, far better than I ever would have expected when we first separated. None of that has much to do with her, though. Without sounding to preachy, I guess what I've realized is that it's up to you to take control of your life - no one else is going to do it for you. You - whoever the f*** you are - are capable of far more than you give yourself credit for. Every second spent dwelling on time lost or time spent is a second wasted - the past is gone, lost in the unrelenting flow of time. Look forward and hopefully you will see a new way to approach your problems. It's up to you whether or not you succeed - the people around you are all fighting the same battle, including your best friend. I realize what I've said here really isn't particularly good and I'm having difficulty finding the exact words to communicate what I'm feeling, but if even a modicum of the passion which I'm feeling on this subject reaches you, then I believe I'll have accomplished my goal.