Who considers the power of your anger,This is really a transitional verse. It is adjusting the thoughts from our perspective to God's perspective. After all of these thoughts on the fleetingness of our days, he immediately jumps to God's wrath, to God's anger.
and your wrath according to the fear of you?
We don't like to make this logical leap. Especially in these modern times that we live in. Any mention of God and angry in the same sentence usually brings up mental images of some backwoods preacher screaming from a pulpit amoungst intermittent deep inhales and a crowd of amens.
Here we see the two ideas tied together by Moses, a brilliant man of God, and a leader of a nation for 40 years.
It is the natural outcome of the consideration of the shortness of men's lives. Why? Think about it through God's perspective or continue reading this Psalm or both.