The Wales coach has demanded the 31-17 win over Italy - Wales’ first for three years in the Championship - has to be a launch pad, rather than a one-off.
"It's a good day to enjoy – it's been a while – but we have to keep growing," said Tandy after only his second victory in his nine matches in charge.
"It was a massively emotional day, a win in the Six Nations has been a long time coming and I am overwhelmed with pride by what this group delivered," said Tandy.
The four-tries-to-three win meant Wales have ended a 15-match Six Nations losing streak that stretches back 1,099 days, since the previous victory against Italy in Rome in March 2023.
It was also first home success in the tournament in 1,491 days since Wales beat Scotland in February 2022 with 11 successive losses following that.
And it was only a third win in 28 Tests for Wales since the 2023 World Cup and a second victory for Tandy to go alongside the one-point win against Japan in November 2025.
"England was a massive lesson for us, we didn't impose anything of what we wanted to do and with panicked with our discipline," said Tandy.
"Since then I believe the boys have grown every week, have got a bit of confidence and had a bit of cohesion as a team.”
Tandy has taken a fair amount of flak for continually stressing that performance mattered more to him than results, even in the build-up to the final game against Italy.
He remained defiant that Wales will contine to focus on trying to perform well, rather than winning.
“I know you think it’s talk, but I genuinely believe it’s performance,” added Tandy.
“Some of the group are growing with experience. We can get too far ahead of ourselves.
“It’s focusing on what we do and what we do well. It’s transferring what we’re doing in training.
“I know it’s hard with some of the results we’ve had. But the group have been unbelievable to work with. I genuinely believe if you get the performance, the result will follow. It’s a great day for us.”
Captain Dewi Lake - who was amng the tryscorers alongside Aaron Wainwright (2) and Dan Edwards - said: “We hope that we have restored some faith in the jersey and into what this group can do.
“I am overjoyed for the boys because of how hard they have worked. That performance sums up how we have grown in the last two to three weeks.
“The scoreline was similar to half-time against Scotland and to come out and score first, to never give up on the moment, to stay switched on and stay in every play shows how we have learnt.
“That was a performance that we have built towards and this group deserves it massively.
“We have gone through a lot of emotionally tough things recently, whether that is on the field or off it."
