Things you should not explain in a cover letter, although you think you need to. Review these carefully.
Writing a cover letter is hard, especially when you have no inspiration. The worst part about it is that you have to tailor your cover letter for each job that you are applying to. Sounds like a lot of work? It is, but there are ways to be smart about it. For instance, you don't have to rewrite your cover letter from top to bottom for each application, but may only need to adjust parts of your cover letter to reflect the specific requirements of each job. With a proper structure, you may be able to replace only the introduction of your cover letter and make some twitching here and there and voila! You have a brand new and tailored cover letter ready to go.
As you write your cover letter, keep in mind that it is not intended to duplicate your resume. Its role is to highlight key aspects of your candidacy that you believe deserve mention. Try to capture the reader's attention enough so that he or she will want to pay closer attention to your resume. Be positive, be personable and focus on what you can contribute to the organization.
The first impression that the recruiter will have of you will be through your cover letter. That first impression can carry you a long way and is your opportunity to put some "personality" to your otherwise impersonal resume. Words talk and whether or not you are interested in the position will emanate from your cover letter more apparently than you might think. That said, pump yourself up before you sit down to write your cover letter and write each word with conviction.