Hiring managers do not want to read an applicant’s life story within a cover letter. At that point they will become overwhelmed with information and the resume may not even be reviewed.
So, the bottom line with cover letters is to keep it short, get to the point, introduce yourself properly, point out a few strong skills and offer a little work history.
Do not get carried away with the fact that you have volunteered with the same charity for a decade (unless that charity directly relates to the job you are applying to) or a narrative on how you like to scuba dive on the weekend.
A hiring manager is not interested in these facts when they have a stack of 100 resumes and cover letters to look through while attempting to find the right person to fill the job.
Cover letters vary in length, but certain guidelines do apply.
Even if you have done absolutely everything the job announcement is asking for, you should not give all those details within the cover letter. That is what the resume is for, and even that should avoid being more than two pages in length.
The cover letter should have an opening paragraph stating what you are applying to, why you are interested in the company, possibly one line listing your strongest skills that would fit the job, and then a sentence stating that you have enclosed/attached a resume for perusal.
The opening paragraph might also note that the resume will “demonstrate accomplishments, such as,” and then begin a bullet point list or another short paragraph.
The second paragraph should either spell out in paragraph form a few accomplishments and/or skills, or list three to four bullet points from the resume showing experience and knowledge that fit the job announcement job requirements.
Search through your resume to find highlights and achievements that are notated in the job announcement, showing a perfect alignment in your work history to what the company is seeking in a qualified candidate.
Once again, keep it short and get to the point.
A third paragraph may be added to restate your interest in the job and the fact that you believe the skills and experience notated on your resume would be a perfect fit for the company.
Lastly, a short closing paragraph of no more than two sentences should note that your contact information can be found on the letterhead (and this should match the header on your resume) and that you are available to meet with the hiring manager at their convenience to discuss the job in greater detail.
When a hiring manager is extremely busy and overwhelmed with applicants, less is more, and they truly appreciate it, therefore developing an interest in you as a person who can get to the point and not waste their time with non-essential information.