God hardwired each of us with a certain amount of self-sufficiency so we could accomplish our daily tasks. However, too much of it crowds him out of our lives while concurrently fooling us into thinking we are doing better spiritually than we really are.
Anything that instills pride can breed excess self-sufficiency, including success, wealth, knowledge, power, fame, beauty, wisdom, physical strength, mental prowess, personal righteousness, spiritual understanding, etc. These attributes are not inherently bad, but they can lessen our dependence on God as they accumulate.
God uses hardship to remind us of his supremacy, our insufficiency and our ultimate dependence on him.