Magic is a mutable changeable thing. It evolves as the world evolves. Changing what works and the ways in which it works as time passes. When humanity lost faith in magic, magic laws shift to take this into account.
If you have tried magic and it failed, to most people that means it is not real. What it really demonstrates is a lack. Whether of ability, Knowledge or belief. You can know the ritual but lack the power to carry it off. You can have no idea what to do but through chance, if you are very powerful and believe, manifest an ability.
But if you fail, then barring outside influence you will continue to do so. Without utter faith in magic and your ability to work your will, magic will only be the illusion the modern world makes it out to be.
– Preamble: Treastise on Magic by Simon Crow
Pelgris 