I Chronicles 28:10 Take heed now; for the LORD hath chosen thee to build an house for the sanctuary: be strong, and do it.
God chose Solomon to build the temple. David is reminding him that God chose him to do a work. He is to be strong and do what he was chosen to do.
That sounds like good advice to all of us. Find out what it is that God wants you to do. Then realize that it wasn’t your choice but His. If He chose you to do a work then you should be strong and just do His will for your life!