The 62-year-old briefly took charge of the Swans prior to Francesco Guidolin's appointment in January.
Swansea had been in the relegation zone when Guidolin came in, but he led the club to a 12th place finish in the Premier League after winning seven and drawing four of his 16 games in charge.
"It's been a bit traumatic considering the success we've had," Curtis said.
"I think we probably lost our way as much as anything, but certainly it is a shot across the bow. It's probably the first season we've struggled for any of length of time.
"But 47 points, and certainly the run at the end there when we had some terrific victories and some really good, strong performances as well.
"We showed that we are still a very, very good team. It's just a reminder how tough this league is."
Swansea sacked Garry Monk in December following a run of win in 11 Premier League games, before Curtis was placed in interim charge.
Guidolin was taken to hospital in March, hours before Swansea's 2-1 win at Arsenal. The Italian also missed their 1-0 win over Norwich after receiving treatment for a chest infection.
But the former Udinese, Parma and Monaco coach recovered to help stabilise the club and will remain as manager next season after agreeing a two-year contract.
Swansea chairman Huw Jenkins has admitted the club's proposed takeover by US investors may not be completed until next season, with the club previously hoping the deal would be done by the end of 2015-16.
"I'm sure that's going to play a big part in what we do as a club in terms of bringing people in," added Curtis.
"I think that probably needs to be resolved quite quickly. We're talking about maybe a little bit of uncertainty again. But it sounds as if it is going to be sorted out fairly quickly.
"We've sorted the manager situation out, we know that we are going to be in the Premier League next season so hopefully there would be a better season to come, not only next season but hopefully the seasons ahead."
Swansea City coach Alan Curtis says the turbulent 2015-16 season was "a shot across the bow'' for the club.