When you say that 'something just goes to show' you mean that it proves your point or demonstrates that something is true. This is a casual statement but it is useful in professional as well as social contexts in order to bring up examples or evidence to support an argument or a claim.

1. Tom's behaviour yesterday goes to show that what I've been saying about him is true. He is not a trustworthy guy.
2. The fact that my car is still running perfectly after all these years just goes to show how well made it was.

1. The success of that awful product just goes to show that you can sell anything with good marketing.
2. Sarah's recent promotion goes to show that you don't have to be a ruthless, nasty person to get ahead in business.