Yesterday's psalter included Psalm 50, which twice refers to the necessity of giving praise to God:
Give your praise as a sacrifice to God (vs. 14)
A sacrifice of praise gives me honor (vs 23)
Why are we supposed to praise God all the time? Is the Lord eternally fishing for compliments, like a beautiful actress past her prime? Does He really need us to tell him how wonderful He is every single day, and be hurt if we forget to do so?
Of course not. If the whole world neglected to utter a single breath of praise for all of history, God would not be hurt or diminished in any way. But we, the non-praisers, would be sadly crippled. The duty to praise God is for our benefit, not His.
To praise God is to acknowledge and be in touch with Reality. To be whole and sane, because we recognize what we are and What God is. To praise is to admire and appreciate. It's a natural response to beauty, goodness, and truth. Someone who had seen a hundred gorgeous sunsets but never felt moved to say "Wow! That's beautiful! Just look at that!" would be suffering from a terrible impairment. (Notice the impulse to say "Just look at that!" Part of the nature of praise is the urge to invite others to praise as well. Which is why the psalms constantly say "Praise the Lord.")
When we recognize our place in the universe--as mere creatures, fallen creatures, who have been miraculously elevated to the status of sons and daughters--praise is the only fitting response. C.S. Lewis says that "In commanding us to praise Him, God is inviting us to enjoy Him."