The word dualism is a big word and branches out to a lot of different sub-meanings. I think you are refering more to what buddhism/hinduism and the gnostic religion (amongst others) are based around. More of a question of spirituality.
I believe the mind and it's imagination are powerful and can influence people to think and view the world in certain ways. It's easy to dismiss something that is external but when it's internal we tend to believe it more.
The question of does our mind exist before or after we are on this earth with or without the body? Is something that has not yet been proven so it's all opinion based for now. Some claim to have memories of past lives.. I... can't explain that. Maybe someone..?
As long as your opinion doesn't make you sad then run with it I say! But of course on the other hand as you get older your view/opinios on life can change/expand (several or more times) so be aware of that!