If she is dead then take time and grieve and don't let anyone say to you that you should be over it. Everyone is different and everyone grieves differently and in their own time. Grieve according to your needs and you'll come out stronger. Don't grieve and you'll be dead in more ways than you can imagine.
If she left, then take your time and look at what the circumstances that happened. Use that to make the required changes in yourself. This will take time and effort on your part. learn to understand yourself and how you deal with each of the little things that come up in life. Finally, don't let emotions rule you (as in letting your heart be given to someone), wait until everything else is sorted out before unlocking your heart.
You need to build strong foundational and broad based friendships first, otherwise, the emotions will grab you, twist you and ruin your life.
I have watched myself, friends, my children and grandchildren let emotions be the drivers of some of their relationships and little good came of it. Those who built on strong friendships tend to make very lasting relationships. I have been blessed that the woman I am married to was and is my best friend in all ways. I know her and she knows me. Everything else has followed.