Saturn as a dominant planet has its bad and good things. On the good side, which also happens to be very good, you'll be aware of your own limits and your environment's, therefore you'll probably try to be self-disciplined in some regard. The bad part is that, given the fact that Saturn is a social planet, its absolute and pure ideals are not usually assimilated so swiftly by our human personality (which is manifested through the personal planets) - the hard reality that Saturn presents us with makes us unforgiving of our failures and shortcomings, which ironically ends up making us carry an even heavier chain of guilt, anxiety and, ultimately more failure. Saturn as a dominant planet is the greatest thing you can have if you're trying to avoid being lazy or not caring about accomplishing your goals.
So the good side is:
Potential for being self-disciplined, hard-working, with good-will, respectable, intelligent (thanks to its connection to airy signs such as Aquarius). It also makes you have a sense of duty, makes you successful. These qualities cannot be given by any other planet. Jupiter, for example, can make you wise and forgiving, but also indulgent, carefree and overall just a lazy person that is bound to never accomplish anything.
Bad side is:
Being too hard on yourself, feeling guilty, feeling constant regret for the past, feeling like everything is a weight you've got to carry, etc. Which as I already said, can make you fail in life. You have to understand that you're human and you've got strengths and weaknesses. By definition, having failed a 100,000 times before in your life does not make you a loser. There is no such thing as being a loser. When there is no shame in losing, there is acceptance, knowledge and further progress. When there is shame but, even so, the attempt to progress, there is unhappiness and more obstacles to overcome.