True happiness is … to enjoy the present, without anxious dependence upon the future. (Seneca, 1st century Roman philosopher)
Worrying about tomorrow takes all the joy out of today. Since tomorrow is uncertain and will have its own concerns, concentrate on today; care for its needs and enjoy its offerings and opportunities.
Therefore do not worry about tomorrow, for tomorrow will worry about itself. Each day has enough trouble of its own. (Matthew 6:34)