Fleeting
If there was one thing Nara Shikamaru had learned in his seventeen years, it was that the people in his life came and went. Some would come back, others he would never see again. And others still had been torn from the world before their time.
And it was from all of these people he had learned the most. He had learned from Naruto that success was not based to power or intelligence, but determination. From Temari he had learned to take the good with the bad, something she was a master of. From his father he had learned to listen and to think, to not assume that intelligence equals a good plan. And from his Sensei he had learned to use his mind, to not idle his life away daydreaming, but to make a difference in the world he lives in.
So yes, the people in his life who were fleeting, who flitted through like the birds in the trees, some staying, some coming back, some never to return again, were the ones who shaped him most.