How to Develop a Large Vocabulary

To do well in languages, we need a large vocabulary. And while I sometimes hear people say, well, I can be fluent with 500 words because 500 words accounts for 60% of most content. But that's not true as the low frequency words and frequency declines very quickly. So how do we achieve that? I think one of the things that can help us is if we accept the fact that we're going to forget - but realize that forgetting is a key part of the strategy of learning.