Reason for optimism: There are easy areas of improvement that are rarely available to a team coming off a 95-win season.
Reason for pessimism: The Nationals squandered Stephen Strasburg's dominance in 2012, Bryce Harper's career year in 2015, Daniel Murphy's in 2016 and two years (so far) of Max Scherzer's brilliance.
In the field of asset management, particularly when it comes to investing in bonds, there's a portfolio construction concept known as a "barbell approach." Let's say an insurance company has a series of payments to make in seven years. It could construct its portfolio to have bond investments with an average duration of seven years by committing half its assets to short-dated investments (such as one- or two-year Treasury Notes) and the other half to bonds maturing more than a decade from now. The portfolio would achieve its goal but be heavy on both ends of the spectrum with little in the middle, hence the description "barbell approach."