Leaders are born, not made, and no amount of training can change this. [1] Please correct my mistakes.

I believe that not all people are born leaders, but everybody can become a leader. Certainly it is very important to have motivation. We can inherit intellectual, emotional, or even physical qualities which can help us to become a leader, but it is impossible to be born as a real leader initially. People become leaders step-by-step. Today there are some training courses, which help people to develop their leadership skills and obtain neсessary knowledge, but the most important thing is persistence and a desire to change yourself. Only in that way can men [2] become leaders more quickly.

I can say that it is easier for those who are confident, clever, sociable and purposeful to become leaders.

[1]  It seems that the title of your post, "Leaders are born, not made, . . . ." is contrary to the body of your post, where you argue that "everbody can become a leader."

[2]  When a sentence begins with a negative introduction, we invert the subject and verb.  Please see Inversion Type 1 at http://www.testmagic.com/Knowledge_Base/lists/grammar/inversion.htm