`position: relative`, `overflow: hidden`, `height: 100%`, `line-height: 1` and `margin: 0` solve a surprising percentage of CSS issues in my experience.
The retort is that you should rely on specificity, by way of selectors.
Good thing that we have the specificity checker, that makes sure that the semantics of your application of styles remain sound if you change the structure of the document in ways that could affect the selectors!