Sun sign or ascendant

[Justwondering]

Hello,

I've had my chart read a number of times and have sagitarius rising. sometimes I feel as though my chart is based on my sun sign being in the first house rather than sagitarius.

My sun is in taurus and in the fifth house. I have mercury in aries in the fourth. However I often feel as though my mercury was in my twelfth house instead - with all th problems that brings! I actually have neptune in the twelfth natal house.

I wonder why this seems to be so. Is there anyone who can enlighten me?

I know how important the sun sign is, but it seems to make the ascendant irrelevant.

Thank you