I do believe in it. I think that our consciousness has a lot more of an influence/effect on what manifests in our life than most people realise. With practice, I do believe that we have the ability to change/manipulate our experience of reality with our minds.
The manifestations of results won't be immediate...they would take time. But I do think it is possible.
Very good point, without persistence we won't get anywhere, because it's the combination of will and time that will transform, we can't expect change overnight !