Don’t waste a lot of time writing cover letters for jobs you have do not have any chance of getting. If there are ten jobs listed in your area of expertise one should focus on the one or two that you are best qualified for.

Writing a specific cover letter to a job advertised takes time, and one should do it thoroughly. It is better to spend the time writing one really good one, than writing ten really sloppy ones. All the sloppy ones may end up in nothing, while if you had written one really good one for the job you were best qualified you may have gotten an interview. It is not good to waste time anyway.

One should dare to apply for jobs you really want even if you are not over qualified for it, but also one should be a bit realistic.