One thing I believe is that both Sag and Cancer are signs that don't really judge people, they accept everyone as they are, so you have that going for you. Venus also rules your social nature, not only your love nature, so again, in public interactions and out with friends, having a fire sign Venus should make it easy for you to click with others, and find topics to discuss. There are quiet Sag people and super chatty ones, so I don't know which you are.
You are correct about the Cancer Moon ruling your inner world. You are sensitive and really listen when others confide in you. But you have to find it within yourself to not let others bring you down. It isn't the Venus in Sag, that should be helpful to you. All of your planets are in a zodiac sign, so I don't know where they are, so I can tell you other sources of help that are in your natal birth chart. It's possible you have more than the Moon in Cancer. Also, being a Sag sun, most of us have a planet or two in the zodiac sign next to ours, in your case Capricorn. Being ruled by Saturn, having a major planet there would make you too serious, or more prone to sadness. I really think that is more the problem. The Cancer Moon you will always have, but planets are always moving. The Moon moves through all twelve zodiac signs in a 28 day cycle, so your Cancer Moon is changeable, and should be a little different feeling every 2 1/2 days. If you go on a site that will draw up a chart for you for free, I'm betting you have planets in Capricorn. It's not the Moon, and Venus is about a lot more than your love nature. Cheer up!