It is so wonderful that your wife was your best friend. You feel really lost, because you think that she is gone, but she's not. She is living inside of your mind and your heart. You have not lost her, she was with you, physically for over 17 years and how blessed you were that you had a great relationship. Now just relax and remember and focus on all of the days that you had together, rather than on the ONE day that she died. If she is your best friend, then I'm sure that she feels that you are her best friend too.
So no regrets, your heart will heal, you won't forget her, she is a big part of your life.
You have what most people are looking for. Someone who loves you, who you love in return. She still loves you, love doesn't die.