How can I positively influence someone?

Answer: Encourage them.

Up-and-coming tennis star Bernie Tomic explains how moved he was by Roger Federer’s words of encouragement:

BERNARD Tomic has vowed to follow Roger Federer’s advice this time and work harder on his tennis over the rest of the 2013 season. Tomic said the advice Federer gave him at the net 12 months ago, were spoken again last night.

“He said, ‘Keep going, you improved’.  Every time I played him, he mentions it, ‘Well done, Bernie, keep going, keep improving’, which is a good thing, hearing that from somebody like him,” said Tomic. . .

“I remember those words.

from Bernard Tomic vows to heed Roger Federer’s advice