Forever in search of job

So far within these past two weeks I have applied for several different nursing positions, only to receive that dreaded email stating that "they" are looking for someone with more qualifications.
It used to be that I would submit a resume and immediately be called for an interview and hired that day.  I suppose those days are over.  I cannot relay to you the frustration over such a situation, but I did it to myself.
When I moved back to Los Angeles from Boston, I was a complete mess, and instead of working on straightening myself out, I jumped into nursing right away.  The problem was that I had nothing to offer my patients because I could barely keep hold of myself.  Therefore, this lead to my demise and I was unable to perform my job properly.
Now several years later, I yearn to help others and I can't because I established such a bad reputation as an employee, that no one will hire me.
What is ironic is that my job is in huge demand, yet no one dare touches me, it's as though I have the plague...rather depressing really.
I continue to tell myself not to despair and that when that one career opportunity presents itself it will be meant to be.  Until then, I am continuing to apply for several nursing jobs that I have great interest in and perhaps they will take a chance on me.
Several times I have kicked myself in the head about the absurdity of the situation, and it's depressing as hell.  Had I just listened to that inner voice and took a break, then maybe, just maybe, I would not be in the predicament I am in.
Like Ulysses S. Grant, who tried on several hats before joining the civil war, I know I will eventually come out with guns blazing!
At times I feel as though I am running an uphill battle.  I often think of General Sherman and how he had to retire from military life due to depression, but eventually overcame those obstacles, and I dare say he did a brilliant job when he re-entered the military.  If it were not for Sherman and Grant, then who knows where our nation would be. *can't help using Civil War references since my research for book is all about it*
I'm not saying I am going to save the country, but if I could help one patient at at time, then I will feel fulfilled, now it's all a matter of time before my shining moment comes and I can once more enter a hospital or facility knowing I can make a difference.