The hardest battle you will face is within yourself.
As the saying goes, it's YOU vs. YOU. You will have people that will help guide you on your path, watching, listening, and following you.
The biggest critic is yourself, motivating yourself daily is the toughest obstacle most people face. Our society has never been as lazy as it is right now, never before has a generation so diligently documented a themselves doing so little (selfies).
If you really want to change you must continuously work on your mindset to become more positive about yourself and what you are doing, life will get that much better.
We all have some brutal winters, days you will want to quit, but when you continue to excel during those winters and can make the most of it. A time will come when the sky's will clear and they are going to be the most rewarding days of your life, reminding you why you started this in the first place.
We all have to deal with our own demons, hardships, betrayal, physical and financial misfortunes. But the most important thing is that I saw a tomorrow.
Believe in yourself and continue to achieve greatness, no one can change who you are except yourself.