Pray and surround yourself with loved ones. God blessed me tremendously in my time of loss with friends who were quick to wrap me up and keep me occupied through the holidays. They were also quite respectful and understanding. No one said a word when I dismissed myself from the table at Thanksgiving so I could go to my room and cry over my loss and my feeling of unthankfulness. They didn't chide me or tell me to cheer up; they didn't invalidate my feelings at all.
My family and friends gave me exactly what I needed: they mourned with me, prayed with me, and supported me. In some cases, I asked to join others. In other cases, they asked me to join them. I didn't spend a single day alone, from the week of Thansgiving to the weekend after New Year's. God provided in a big, big way.
I was praying a lot, and reading the Word a lot, as well. That might have been the only thing that kept me from losing my mind. I know that the most difficult thing is to try to not think about her and what she's doing without you, but instead, focus on God, and He is doing with you, and what He has planned for your future.
Blessings to you, brother. You are not alone in this, no matter how you feel, so long as you continue to fall on Him. You might not be able to feel it right now, but He's holding you tightly right now.