When looking for books, you want to keep your search focused on the most important keyword or phrase, without using too many keywords.
In larger databases to find articles, you can use more keywords in your search. When reviewing your results, look more towards relevance than quantity. If you are finding sources which fit your needs, your search is going well -- even if you're retrieving thousands of records! It's very rare to craft a search strategy that brings a small list of perfectly relevant results.
Search strategies to try: