First and foremost, Congratulations on your commitment!
Although there are many up's and down's in the Flying industry, you will find this in every profession worldwide, so try to keep a long view to your hope's and dream's.
I think having, and keeping, a positive attitude will be your most valuable asset. It will help you work better with others, and in the Flying world, this means everything. Whether it is during a Type rating evaluation or sitting next to your fellow pilot for twelve hours, keeping your thoughts positive will really make a huge difference.
I wish you the best of luck!
