It may be hard, perhaps impossible to know and understand all things. Because of that, faith is necessary to have direction. Those who truly have chosen to have faith in having no faith will have no direction.
If we do choose to have faith might as well have faith in something good, for example, faith that if we do good things in life, more good things will happen, while not necessarily the good things we may have thought would happen, over all, good things, perhaps unexpected and better.
What is faith? Faith is our philosophy of life, our reason for life. Whatever our reason for life is, becomes our guiding star. No matter what our decisions in life, we consult our guiding star, our mission in life, to see how our choices will effect our view of that star, and the star itself. We try not to make decisions in life that will hurt what we believe is right, that star, that faith. Though it may seem as though we will never see the final result of our actions through faith, each decision in our life we make in accordance with making that star shine brightly, becomes an accomplished mission.