Jesus said to his disciples: “The person who is trustworthy in very small matters is also trustworthy in great ones; and the person who is dishonest in very small matters is also dishonest in great ones." (Luke 16:10)
We are called by Christ to lives of virtue. Virtue is the habit of doing the good. Over time our souls and our wills become accustomed to doing what is right by the regular practice of choosing the good in small matters. Then, when big questions arise, we are already accustomed to choosing the better path.
Vice is the opposite path where we habitually choose sin or avoid doing what we know is right because of fear or sloth. In this our flabby, out-of-shape souls are not strong enough to rise to the challenge. So follow Jesus' plan and begin with consistently choosing the good in small ways. These "spiritual exercises" are a necessary part of the Christian life.