A superstitious person believes he or she needs to avoid some things because they're "unlucky" -- such as certain numbers or dates, or certain activities or animals. Other things (they contend) are "lucky" or can bring them good fortune. And you're right: It's not logical for someone who denies the existence of God (or any spiritual power) to be bound by superstition.
Sadly, superstitious people often become so absorbed by superstitions that their lives are ruled by them. Instead of enjoying life, they live in fear -- fear that they'll do something wrong and bring misfortune on themselves. Others constantly pursue things they hope will bring them good fortune -- usually in vain. They may even become involved in occult practices, which can bring them into contact with spiritual powers that are opposed to God.
The Bible tells us to avoid such things, however, and to trust our lives into God's hands. God loves us and watches over us -- and once we understand this and commit our lives to Christ, our superstitions will flee. The prophet Isaiah condemned the people of his day because they were "full of superstitions... and clasp hands with pagans" (Isaiah 2:6).
I can't help but wonder how your boss would answer your question. He might say (as some do) that the universe isn't ruled by active spiritual powers, but by impersonal laws he's trying to follow. But in reality he has let his superstitions take the place of God. Pray for him, and ask God to help you be an example to him of Christ's love and grace.