To "watch over" something means to guard and protect it. But "watching over" something is not as serious as "guarding" it. A professional "guards" things like expensive artwork, an empty office building, and so on. But regular people can "watch over" things like someone's computer or someone's teenage child.

People often say that God "watches over" people as well:

God, we pray that you watch over Richard and his family in this difficult time.