Thus have we heard from Bill "The Ferret Meister" Keyes:

Karma is when that if you were bad back in ancient summaria, then you're
going to be hit by a meteor soon.  And if you are bad now, then when you
die, then your mind-stream (that is, you don't actually have a soul, and
you aren't really anything that can be nailed down, so it's not really you,
but it's the results of what you are now and were in the past, that is,
that it's not you, or your mind, or your body, or your emotional self,
or anything about you really, but it's this continuation of you that exists,
somehow, outside of time, that doesn't really exist in any way, but in the
end it turns out to somehow be the essential you (which as you know doesn't
actually exist in any form or sense) that exists and continues throughout
time) is re-incarnated in a lizard.

This continues to happen, over and over.  Though it really isn't happening,
because there is no "you" to exist through time, since there is no abiding
soul.  But anyway, you (well, sort of) get re-born over and over, in order
for the universe (which also doesn't really exist) to punish you.  Because,
as we know, if you do bad things, then you will pay for them.  Even if you
don't pay for them in this life.  You'll (sort of you) will be re-incarnated
as some miserable creature for X lifetimes, where you will have the benefit
of accruing good karma (though the karma you accrue isn't really yours, since
there is no "you," so to speak.  Just, as I said, a sort of abiding, continual
non-abiding thing called a mind stream which exists apart from both you and
time).  And if you accrue enough good karma (within the limitations I've
just described) then you will be reborn, not as a lizard, but maybe, if you're
lucky, then something better, like a human.

Though better really isn't a good term for it.  Because then you will again
begin to accrue (not really) more bad karma.  Or good karma, which is actually
bad karma, too.  Because all karma is, in the long run, bad.  Because if you
keep collecting it (well, since there's nothing to collect it, you can't
really, but you do anyway, as there is something (not really though) that
abides throughout time and space: cf Rebirth) then you will be reborn again.
Because, as I said, the universe has to punish you.  Or reward you.  If
you were good.  So you keep coming back to be punished or rewarded.  But both
are really punishment, because... well, just because you have to keep coming
back.  And the odds are, you'll generate more bad than good.  And if you
generate bad karma, then in some future life (which, of course, isn't really
you, though it is) you'll be hit by lightning.  Punishment, you see, for
all that karma you accrued.  Or didn't accrue, as you can't really, since
there's nothing to be accrued or to accrue.

So, in a nutshell, you were a bad boy.  And whenever something bad happens
to you, it's the universe getting it's revenge on you for something that
you did while you were a lizard, which happened before you were born as a 
human, though it wasn't really you.  Just your mind-stream.  Which is sort
of you, but not really, since there isn't any you.  And because of this,
you'll be reborn as a lizard again, sometime in the future, after you die.
Though I must stress once again that it's not really you.  No abiding self,
you see.  But it is you, in fact, because of cause and effect.  You'll have
to be punished, and if it doesn't happen now (or maybe even if it does),
you will be sooner or later.  In another life.  That isn't really you.
Sort of.