If you try and focus on one part of the spectrum, you'll be weak on the other part. If you're good at right, you'll be weak at left. If you're good at left, you'll be weak at right. If you try to conquer both the right and left, you'll be weak on both.
We all have our personal preference. Some of us write with right hand, and some of us left. Anyone who writes or uses right hand to work will be better at it. If that person attempts to work with left hand, he will have difficulty. His work with left hand won't be as good as his right hand.
A person can't be good in everything. If he tries to, he will fall on all level.
So, it's important that you realize what you want to conquer. You should have a goal in life (life goals) - it's vitally important. A person without goals fall into the vicious cycle of failure.
Most of the time, it's clever people who fall. They try and conquer everything at once, which will make them fall on everything.
Having a goal is like having a side of your preference. It might be right or it might be left. It's you who should choose. And if you are not aware which you choose, then you'll never be strong.
You can either set a goal and master it, or choose many goals and be an average.
It's important that you work and master something, instead of working on everything and being mediocre on all level.