Repeating a link will not cause extra PageRank to be passed to that page, nor will it cause link juice to get lost.
Google usually only pays attention to the anchor text from the first link.
If one of the links has a rel nofollow on it, then Google treats all the duplicate links as if they were nofollowed. (Why should they trust any if you say they can't trust one?) So don't try to use nofollow to tell Google which of the duplicate links it should pay attention to.
Adding a different anchor to each link (
#anchor) causes the duplicate links to be de-duplicated and Google passes PageRank and anchor text to all of them. It is unclear if this then helps the full target page, or just sections of it.
Links with nofollow and links to pages that are disallowed in robots.txt do cause your site's pagerank to evaporate. In practice, that doesn't seem to matter much. Rankings don't drop when nofollows are applied to unimportant internal links, nor do they improve when they are removed. Google seems to have some way of compensating sites where a large portion of the internally passed PageRank evaporates.