Your Cancer Sun means you are a changeable person who comes off a little bit reserved, but warms up to people as you get to know them. The Ascendant is the way you SEEM to those who don't know you, the facade you project. So again, you may seem nurturing and kind, while giving little else away to others to protect your gentle sensitivities. You are a natural leader, but it takes others a long time to figure that out. You are generally well-liked and nice to people; you don't want to hurt anyone's feelings. You are family oriented and probably a hopeless romantic. You have artistic abilities in whatever is your area of interest.
Most Cancers need quiet time and like to get away from others now and then. Solitude and meditation are good for you, but at times you are lots of fun and are a social creature. It depends on your changing moods.
The 12th house is the last one, usually called the house of secrets or sorrows. So you may have lost something or someone who you loved very much, or they could have been a thorn in your side all the time. This could also be a family member, since Cancers are so family oriented. Having a Cancer Ascendant, you probably have Gemini on the cusp of the 12th. I can't be positive without drawing out a chart. Is there a Gemini in your life who is the bane of your existence? Hillary Clinton's Sun is in the 12th too, and she lost out on the Presidency of the US two times. Have you had a wish and been denied something really important to you many times? The Sun here can also mean you have spent time in a hospital for many illnesses or work in one, or been in jail for some reason, or work in a large institution, as places like that are ruled by the 12th house. You could also need such a large amount of solitude that you live like a hermit for long periods, but being Cancer, that will change when you feel like going out again. You have secrets.