Following a loss, the person grieving has to face important days without their family member or friend. Important celebration days like Christmas, New Year and birthdays have to be faced.  These days are a sore reminder of your loss and form a marker of the passage of time since you last saw your loved one.  

You acknowledge each of these milestones even if they are painful.  Gradually you will be able to look back at photos or videos of earlier special occasions, though that takes time.  In the early days the feeling of loss is so painful it can be hard to look at the reminders.

It is difficult to focus on the world at large.  Most of your thoughts will be focused on your own small world.   Other issues seem irrelevant.  Gradually with the passage of time you widen your focus back out again to the wider world.