My boyfriend is very tired at work and the weather is cold. What should I say to encourage him to relax and drive at the construction site?

You don't have to say anything, you just need to be with him when he is tired. Pay attention to some details in life, care more about him, and let him feel warm at home, so that he will be motivated. A man who is willing to work hard for you only needs your warmth, knowing that you care about him and love him is enough.