We generally like to take comfort in the fact that God loves us and is intent on providing for our needs. But the psalmist was well aware that God was not obligated to do so. He owes us nothing. He has His standards. God is always good, but He does not bless indiscriminately.
One of the most sobering realities is that God blesses us based on what He finds in our heart. We desperately want to believe that we fool Him with outward appearances just as we think we mislead others. We hope that God somehow overlooks our shortcomings and sins, as if He chose to use a lesser standard for us than He applies to others. But that is wishful thinking.
God looks to our heart before He dispenses a blessing. The single greatest thing we can do to ensure our well-being is to guard our heart.
We can be confident that God is good. We cannot be as sure of our own heart.