Certainly 2000, 2001 and 2002 come to mind and are the most obvious. I was confident in 1978 after they canned Ground Chuck and promoted Malavasi. I was sure Elvis Peacock was going to thrive on the Rams. I was confident in 1987 after making the PS with rookie Everett in 86 and having E.D. but the damn strike ruined that. I was confident in 1990 after getting to the NFC Championship Game in 89. I was confident Fisher had us on course in 2013, because 7-9 in 2012 felt like 12-4 after years of crappy football. I was confident in 2018 after McVay's rookie year and Goff's steady improvement*. Definately in 2019 and I was confident last year. This year seems promising with Stafford and the defense.
*A note on that 2018 season. I re-watched the Vikings game and the KC game from 2018 yesterday and it made me wonder, "what went wrong with McVay and Goff"? Or more accurately, when. They were 15-5 after the Minnesota game and 20-6 after the Chiefs. They were chest pumping, all smiling and giddy, looking like the newest shiny NFL Maserati. Man how quickly things change. And that tempers my confidence for 2021. I'm confident but I also know I've been confident before (whether rightly or wrongly) only to be hugely disappointed. But I hold solace in the fact I'm not hoping to be .500 or 9-7.