Can someone explain what Psalms 1:1 means?

You'll be happier if you don't spend a lot of time with unbelievers. You will be joyful if you stay focused on the Lord and read the Bible a lot. You will have a productive Christian life and not waste your time. The life of an unbeliever comes to nought. They will not receive any rewards on Judgement Day. God remembers our service to Him, but unbelievers will be lost forever.