Looking inside my soul

Let's see...
* Business is not exactly flourishing, but it is definitely looking up and
the potential is clearly present.
* I have a business partner who is young, smart, committed and patient with
me.
* I have a good amount of money coming in.
* My better half is very, very supportive of everything I do.
So why I am I slipping into the mode that I fought successfully for two
years - the mode of sloth, depression and self-doubt. Why is it that the
drive that I possessed for two years is disappearing?
I need to understand this well - I am pretty much in the midst of
reinventing myself, trying to be a better man that I used to be, and it has
been a long haul with a lot of sweat and tears. But I have learnt many
things, have discovered both good and bad things about myself.
Let me enumerate some of the good things:
* I am smart
* I have a "can-do" ability; I can accomplish things that others think are
just not possible.
* I don't complain, I act
* I like to help people
The bad things:
* I have too easily prone to depression and lethargy
* I can often lose focus
* I often shut up and swallow crap that I should directly reject
* I am prone to bouts of self-doubt
So now, why am I getting so caught up in my own underwear, stumbling along
through the days that can be used to do a whole list of interesting things?
I am currently very unfocussed, but am unable to fathom why. And this
attempt to logically dissect myself and figure out what's wrong has
floundered as well...