When you start training, you obviously want to do everything
right so you can make gains. You also want to strive for
constant improvement. Unfortunately, that yearning for
improvement can lead you to commit training mistakes that
hold you back.
Sometimes knowing what not to do can be as important as
knowing what to do. Avoid these mistakes so you can
prevent
injury and get better.


1. Ignoring the Negative

Negatives are important in training. I'm talking about
lowering
the weight—i.e., the eccentric portion of the movement. Let's
use the barbell Curl for example. Curling the weight up is the
concentric (or positive) portion of the lift. The eccentric part is
when you lower the weight to the starting position.
Just
allowing the weight to drop and letting momentum and
gravity
do the work for you will impede your progress. But when
you
control the weight on the way down, your muscle fibers tear
down. As lifters, this is what we want, because when we eat
and recover, the fibers rebuild so they will be prepared for the
next workout.
This is the progress we are looking for.
Ignoring the negative on your lifts means you're not breaking
down the muscles as much as you could be. They don't have
to work as hard and thus, you won't see improvement.


2. Focusing Too Much on Weight

As exciting as it is to see the numbers going up, the
dumbbells
getting bigger and more plates being loaded on the bar, your
focus as an athlete should not be on the weight itself. Doing
so
can lead to an inflated ego and possibly a serious injury.
The
weight is a tool, a means to an end. You should focus instead
on working your muscles sufficiently. Using our barbell Curl
example again, instead of focusing on curling 100 pounds by
any means necessary, work on contracting your biceps
without having to recruit other muscle groups to assist or
swing the weight.
You might have to drop the weight down to
60 or 70 pounds, but the result will be bigger and stronger
biceps. If you apply this principle throughout your entire
training program, you will benefit both in the weight room
and
on the field.


3. Failing to Stay Hydrated

Yes, in 2014, I still see countless athletes making this mistake
in gyms and on fields. Training for a long time without a
water break does not make you tough. When you're
dehydrated, you become susceptible to dizziness, lack of
focus and a decrease in athletic performance—and this is if
you're only slightly dehydrated. It gets worse as you become
more dehydrated.
You may develop migraines or fever, or faint. How can you
tell if you're dehydrated? If your urine is bright yellow or
amber-colored, get water immediately. I always recommend
athletes take in one gallon of water a day.

Source- www.stack.com/2014/12/02costlyworkout-
mistakes/?utmsource=yahoo