There are some people who refuse to accept any level of certainty at all. That's okay for them. Personal passion is not a lifestyle choice. A metaphysician however, tends to be very passionate about life. The excitement, wonder and mystery of playing games with the Universe is irresitable.
Passion is part of it.
Certainty can involve a type of passion as well. It involves more of the Self than being a disinterested bystander does. Take the risk and let yourself know with certainty that life is good and that you can experience your dreams in the here and now. A man is happy so long as he chooses to be happy and nothing can stop him.