There is a chapter in Joseph Campbell's The Hero with a Thousand Faces where he describes the "meeting with the goddess:"
The ultimate adventure, when all the barriers and ogres have been overcome, is commonly represented as a mystical marriage of the triumphant hero-soul with the Queen Goddess of the World. This is the crisis at the nadir, at the zenith, or at the uttermost edge of the earth, at the central point of the cosmos, in the tabernacle of the temple, or within the darkness of the deepest chamber of the heart.
This is a pivotal moment in Campbell's "monomyth" of the Hero's Journey, which concludes when the Hero (or Heroine) returns home with a greater understanding, knowledge, and perception of the world. In Campbell's words, the Hero "finds their bliss."
Following your career path is your own Hero's Journey. You start off with the call to adventure. You find friends along the way to help you. Some days are fraught with challenges to overcome. You may be faced with a crisis of identity. Finally you meet the goddess--the one handing you the talisman that will allow you to attain the career you want. Face to face with the goddess, what do you do? Hand her a cover letter with your resume and hope for the best? No.
There are very few opportunities for shortcuts on this journey. This adventure requires patience, commitment, and perseverance. It comes back to research, networking, and preparedness. It means making connections. Your heroism should precede you; the employer should be curious to know who you are before they read the resume and cover letter.
If the resume is your history, the cover letter is your story. It brings the reader to the present, looking forward into the future. It tells them who you are as a person, and the journey that you're on. There is no looking back--no need to rehash what's in the resume.
Setting aside the romantic, you need three components in a cover letter:
Why you are interested in the position, what motivates you, and what your values are.
Their story. What you know about them, and why you believe in what they do.
How your values are synchronous with theirs, and how you can help them succeed.
Keep it short. Have a friend read it. Make a version for every position you apply for. If you can't find who the position reports to, find a key person that is a point of contact. "To Whom it May Concern" might as well be the trash can. If you're still stuck on ideas, formatting, and focus, I recommend again the Guide to Rethinking Resumes by Richard Bolles.
You've come far enough to find the position you want-- you can't leave it up to the Fates. You need to meet the goddess herself. Then--and only then--will you find your bliss.