Losing someone is a bit hard on your stress. It is healthy to cry about it even if it happened weeks, months, or years ago. You are still hurt by losing a loved one. The best thing for you to do is realize and know they are in a better place, and they are at peace now. Cry it out, Hun.
My grandfather died a year ago in July. Grieving is healthy, but becomes unhealthy if you let it. I believe you can grieve as long as it takes to heal yourself. I know it will take me several years to get over my grandpa, and I may never get over it. But one thing you need to realize is that unhealthy grieving is the type that takes over your life. if you feel yourself becoming depressed, seek help. Do not let the loss of your loved one become so apparent that you cannot succeed in your own life. Your friend is looking down on you hoping and wishing you live a long happy life. I know it. Every time you have an achievement they are up there smiling and telling everyone else up there "THAT'S MY FRIEND". Make your friend proud(:
I lost my best friend to suicide 2 years ago. There are still times when times when I breakdown, and have to go home and cry. After it happened, I didn't go outside for two weeks after, and it was a long time before I felt better. Everyone deals with grief differently. It only becomes unhealthy if you let it consume your every thought. Losing someone you love is never easy. What got me through were my other friends. We remembered all the good things. Try talking to someone else about what you're feeling. Just remember that time does not heal all wounds, but it does helps us find new things to fill the holes in our lives.