Right Person

It is a weird one but sometimes people do not act the way I expect.  I am thinking about this as it is not what I am going through but what someone has related they went through.
There are times when someone is just not right.  There may be no question that the motivation is good.  The desire to assist is without question but the task is just not their thing.  Those are the hardest to kindly suggest something else may be better.  For me nothing is no ones thing.  It is always a case of marring the right person to the right task.  It is not always possible but it is my belief it is better to have no one then the wrong person.
The first question I think I need to ask myself is, were my expectations made clear?  Without a clear set of guidelines people help because they want to, but they do it as they know to do it and always have.  Their abilities and their desire to do the right thing are not lacking, but my ability to communicate my expectations are.
My thinking is it is necessary to show in the first instance, do together then allow a person to do and answer any questions along the way.  Often there is a feel for what is the case early on.  Yet where possible no action should be taken until something is proved one way or the other.
In my last job I employed someone and on the first day it was like “what have I done?”  Yet that person turned out to be the best worker I could have ever hoped to have.  How something starts is not necessarily how something will end.  I often think of sailing boats.  A correction may be needed to have someone head in the right direction, but once it is made there is no stopping them (except at the finish line hopefully.  Otherwise they are still out there somewhere.)
For me, a person needs to be given a chance.  I know I would want that for me.  The tendency seems to be to quickly write off.  Yet if I do that, I may be the one who misses out big time.  Yet if they do not turn out I do not believe it is right to keep them doing the task if possible.  There may be someone waiting in the wings who is the right person for the job.  Me keeping someone on who is not suited to the position is robbing the person that is right.
Besides they may go somewhere else if given the opportunity.  In one position I was in, I was told by the boss I was wanted for their position.  After more than 10 years I ended up going elsewhere.  I felt the position would never become available.  I heard the other day they are still going in that position.
Honing my skills while waiting is one thing.  Seemingly endless waiting is another.
My experience in getting the right person for the right position is both theoretical and practical.  It is not recent, but hopefully I am ready if it comes.