As Swami Vivekananda once said: Learn concentration and use it in any direction. Thus you lose nothing. He who gets the whole must have the parts. Who
is to wonder that concentration is essential in spell-casting as well?
As concentration is important in everyday life, it certainly has an
effect on magic as well.

I must admit
that I was relieved that concentration is not necessary for each and
every spell. Maintaining the focus on a lot of things for a longer
period of time is really exhausting! And you mustn't lose your focus on
what the things are meant to do while practicing, else it's going to go
awry. This is definitely a thing that I will need to practice for some
time, as to make it work reliably. A comic that we were shown some time
ago is actually quite accurate as to my ability to concentrate for a
longer period of time.

http://explodingcomics.com/wp-content/uploads/2012/06/2012-06-25-Drawing-in-Classes.jpg

Well,
this is not the way that concentration is supposed to work, is it? But I
was told that concentration would be a matter of practice, and that it
would become easier after some time. Hopefully, that's right. I'll keep meditating anyways, just to be on the safe side.

The
applications of concentration in charms are simply amazing! Ever since I
heard about concentration being necessary for the Patronus Charm,
maintaining enough concentration moved up quite high on my to do-list.
The Patronus is such an interesting charm, and I would love to be able
to cast it in a couple of terms! I would love to know what its form is,
it's supposed to be symbolic, this would be so interesting to know!

I'll definitely spend lots of time with the Dancing Lights Charm, this should be a great practice for concentrating!