Many things happen in our lives simply because we sin or because we do foolish things. We receive the natural consequences of our sins as well as any punishment that God gives us because of it.
Life is filled with chance events. We might run into someone we haven't seen in a long time. But that doesn't necessarily mean anything. It certainly doesn't mean we should leave our spouse for someone we used to be with just because we met them by chance.
The Bible never says that everything happens for a reason.