The Norwegian took over from Neil Lennon last summer but after a rather frantic pre-season and while still getting used to his squad - and they to him - two chances to reach the group stages of the Champions League were passed up.
After losing 6-1 on aggregate to Legia Warsaw, Celtic were reinstated due to an administration error by the Polish club but contrived to lose the play-off to Slovenian side Maribor.
However, Deila slowly put his stamp on the club and guided the Hoops out of the Europa League group stage before they were beaten 4-3 on aggregate by Inter Milan in the last 32.
And after domestic dominance was established, Celtic captured the Scottish League Cup in March with a Hampden win over Dundee United and were confirmed as Scottish Premiership champions at the weekend when challengers Aberdeen failed to win at Tannadice.
Deila, speaking at Celtic Park ahead of the trip to Pittodrie on Sunday, used polemic to sum up his first campaign at the Glasgow club.
“It has been an unbelievably good experience for me,” he said.
“It has been tough at times and very happy at times and that’s why you love football.
“It is hell or heaven and you have to be used to it and you have to love having sh**** times and to turn it around and be happy because it is never something in between.
“It is always very good or very bad. (The hell times) is easy to answer.
“The first six month was very tough. The Champions League (qualifying) campaign was very hard.
“I didn’t feel so much a part of it but I had to manage it.
“That was the tough part of course, as well as the beginning of the season when we struggled in the league.
“We lost 15 points (before New Year) and we lost five after that and that’s what makes me happy.
“The Europa League is not talked about so much but it was a big thing to get through the group stages and play European football in winter.
“The two games against Inter Milan were some of the highlights of the season and we deserved more in those two games.
“Things are improving and I am eager to take it forward to the next stage.”
Indeed, the former Stromsgodset boss believes he and his squad will be much better placed next season to qualify for the Champions League.
“We are in a totally different situation than the one we were in last year,” he said.
“The most important thing is keeping players. We need consistency and the players here are good enough to take us into the Champions League.
“But we need to make the squad stronger and make it more competitive.”
Deila appeared relaxed about loan defender Jason Denayer returning to Manchester City.
However, he urged his Dutch centre-back partner Virgil van Dijk, linked with a number of clubs including Arsenal, to stay at Parkhead and prove in the Champions League that he is good enough to join one of the elite clubs in Europe.
He said: “Denayer goes back to Man City and we have to look at what we do there, that is a challenge.
“But there is more in it for us to get into the Champions League than to sell Virgil van Dijk.
“Virgil also needs a good Champions League campaign and if we get into the group stages he will get the challenges he is after.
“He is a very good player but still we can make him better.
“He should go to the biggest clubs in the league, not the small clubs in the biggest leagues with money.”