Aaron is an architect at Wayfair. We don't want to say he's old, but his experience dates back to a time when SQL Server 6.5 was considered "modern." He writes here at sqlperformance.com, over at sqlblog.org, and at MSSQLTips.
I see a lot of advice out there that says something along the lines of, "Change your cursor to a set-based operation; that will make it faster." While that can often be the case, it's not always true. One use case I see where a cursor repeatedly outperforms the typical set-based approach is the calculation of running totals. This is because the set-based approach usually has to look at some portion of the underlying data more than one time, which can be an exponentially bad thing as the data gets larger; whereas a cursor – as painful as it might sound – can step through each row/value exactly once.