Grieving the loss of a loved one is always hard - and we make it harder with the expectations we place on ourselves. All too often, people who are in mourning fear that there is a "right" way to process their emotions, then kick themselves when they fall short of that standard. The grief journey is made exponentially more grueling by this sense of failure - the idea that you're somehow not measuring up.
The first thing you should know about grief is that there's no one right way to do it; all of us express emotions differently, and that has everything to do with the way our brains are wired, nothing to do with how much we do or don't love the person who passed.
For example, some people may cry throughout the mourning process, while others don't shed a single tear. Both are completely acceptable ways of dealing with bereavement. Similarly, some may want to be surrounded by friends, never to be left alone, while others may crave solitude. Again, both approaches are reasonable and natural.
One caveat to this: There's no "right way" of dealing with grief, but it's important to ensure that your bereavement doesn't compromise your physical health, either because you stop eating, stop sleeping, or fall into self-medication. Additionally, dealing with grief means allowing yourself to feel and experience it. Trying to ignore your mourning, or to bottle it up in some way, can ultimately be self-destructive.
Take care of yourself, and channel your heartache through positive means - but don't let anyone make you feel like your expression of grief is inadequate. That's not going to accomplish anything but making your bereavement more difficult.