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."

Three policemen were shot dead by suspected al-Qaeda members in a village near the border with Burkina Faso.
One soldier was killed and two others wounded when a military convoy was attacked close to Nigeria's border.
Thursday's attacks came three days before Sunday's controversial presidential run-off election.
The opposition has said they will not recognise the results of the vote, and their candidate Hama Amadou, is currently receiving medical treatment in Paris after spending months in jail.
Niger's Interior Minister Hassimi Massaoudou says the attack in a market in Dolbel village close to Burkina Faso was the work of al-Qaeda in the Islamic Magrib (AQIM), which has been active in the region.
"The attackers were repelled, and we are currently sweeping the area," he told the AFP news agency.
The other attack was carried out by four suicide bombers in southern Diffa region that has often been targeted by Nigeria's Boko Haram insurgents.
A fifth suicide bomber, a young girl, was prevented from detonating her vest, Mr Massaoudou added.
Niger has porous borders with Libya, Algeria, Mali and Burkina Faso, which have all been hit by AQIM recently, and Nigeria to the south - making it vulnerable to Islamist attacks.
The country is rated by the UN as one of the world's least-developed nations and was recently named as the worst country to live in.
Swansea City coach Alan Curtis says the turbulent 2015-16 season was "a shot across the bow'' for the club.
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Islamist militants from al-Qaeda and Boko Haram have killed four security forces in two separate attacks in Niger, officials have said.