Andy, I lost my Dad suddenly last year. My mom was rushed into hospital last week and I was told to fear the worst (thankfully a false alarm) A couple of prominent members on here have also lost close relatives in the last year as well.
How you are feeling is perfectly natural / normal after such an event. Some days you will feel good and others you will question why you are bothering to to anything in this world... a kind of "what's the point?" approach.
I think it is important to realise when you are having a bad day and make allowances.
I left the hospital a couple of days ago knowing I had to build a couple of websites and write some advertising copy. I know now not to do anything "creative" on a bad day because I will mess it up. Instead of working I went for a long walk. Maybe it is best to look at your business when you are feeling Ok? On a bad day, go and do something physical (work, exercise, whatever). It's OK to feel lousy now and again. Just be aware that it may affect your outlook or judgement on that particular day.