The New Zealand-born wing's 10th-minute try gave the Scots the lead yesterday, but a first win at Twickenham in 30 years proved beyond the visitors as England lifted the Calcutta Cup with a 38-18 triumph.
Sean, who joined Glasgow Warriors in October from the Crusaders, knows Scotland have plenty of room for progress.
"You can't be negative," said the 24-year-old, who qualifies for Scotland through his paternal grandparents.
"You've got to be positive. There were heaps of positives: scoring tries and staying in the game.
"But you've got to look at the things you need to work on. There are a lot of things that we need to work on, let's be honest.
"It's just a shame we didn't do the jersey justice; all the boys are very disappointed."
Sean and his back-three colleagues Tim Visser and Stuart Hogg, who was influential in the opening try and scored Scotland's second late on, were peripheral figures as England dominated for much of the match.
On the few occasions they were involved they showed their potential to trouble any opposition.
The Warriors wing hopes he has done enough to retain his place against the Azzurri in the first of three successive home matches.
"Things have gone really fast for me," said Sean, as he reflected on his Test debut.
"I've only been here for a couple of months. To be playing Test rugby for Scotland is a dream come true.
"It's just the start, hopefully, for me. Going back home to Murrayfield is going to be special. Hopefully I get to play and experience Murrayfield for the first time.
"I've still got a lot to prove to the people of Scotland, getting selected having not been in the country for long.
"I scored my first try in my first Test. I was happy with the first 10 minutes but the next 60 minutes I wasn't too happy.
"There's a few things we need to work on. The tackle area and getting our backs involved. We (the backs) were a bit of a myth out there.
"We were more frustrated, all three of us. There's a lot of talent to be shown in our backline. It's just one of those things."
Stuart Hogg's display impressed Scotland coach Scott Johnson
"Stuart (Hogg), it was the best game I've seen him have in Scotland colours. I thought he did wonderfully, wonderfully well," said Johnson.
"It shows what a great talent he is and we like to get him in positions. You can ask me 1,000 questions, the reality is yes, we can beat sides, we can look good. We'd like to look good more often.
"We want to play an attractive game of rugby and we've got potent players to do it but we are limiting our chances unless we get it right.
"We've just got to keep repeating that work. It's not a lack of will. This team has got a lot of will."