First, let's layout the operational definition of what an attitude really is. Attitudes are habits of thought that govern the way you relate to people and situations.
Attitudes are the lenses to how we see the world. If I think others are untrustworthy, than I'd be an untrustworthy person. If I think the world is against me, than it will be.
Conversely, If I think the world is full of possibilities, than it will be. So the point here is to have a positive attitude, which will guide you to positive outcomes - guaranteed.
We're like mirrors that reflect upon one another - so it's up to you as to which lens you want to apply. For bonus points, try not to choose a lens at all and watch what happens. Buddhist monks call this the lamp effect. When we clean off the dust off of our lamps - we see and experience the world as it should be. No bias, no preconceived notions or past generalizations to stain the moment. I think positivity will be your end result.
Inevitably though, dust (like everyday life) will begin to collect. So what's the best way to keep our lamps clean?