First, they impact how those around you function. Second, they also impact how others choose to view you. Ned is a nay-sayer. He can find the negative aspect of any situation even if it requires looking all night long. Ned views the world as a dark and dangerous place.
Every decision is monumental.
Each life choice must be painstakingly scrutinized. Consequently, Ned spends much of his free time worrying about the 1001 bad things that might happen to him at any time. Oscar, on the other hand, is an optimist. He sees each day as another opportunity to be successful and help others. The idea of doing something new and different excites Oscar because he likes to contemplate and explore all the interesting possibilities in life that are placed before him.