Some days hold a lot of pain or struggle. At these times, we physically learn the truth about how dependent we are on God for our needs, even our qualities, our strengths, and our existence. We learn to trust His ways with us, and as we cling to Him we know His love and we love Him.
Other days are full of joy and clarity. This gives us a chance to experience the flip-side of the same precious thing. By remembering our Maker, by knowing there is only one power in the world and by pouring our gratitude out for Him, we again see clearly the truth that all our desires, all our joy, are literally nothing away from Him. And so we can put things into their place, and even the highest joy is given its true beauty and sanity when it has no power to sway us from the one we look to as our God. Thankfulness is also joy!