The 46-year-old, in his third season in charge of Barca, was speaking after their 6-1 win over Sporting Gijon.
He won the Champions League as part of the treble in his first year and led them to a domestic double last season.
But they are on the verge of elimination from the Champions League after losing 4-0 to Paris St-Germain in the last-16 first leg.
“It is a difficult, measured and well thought-out decision and I think I have to be loyal to what I think,” said Enrique, who will leave at the end of his contract this summer.
“I would like to thank the club for the confidence they have shown in me. It’s been three unforgettable years.
“It’s about how I live with my profession, with a never-ending quest for solutions and to improve my team. That means I have very little time to rest, very few hours to disconnect.
“I think it will be good for me at the end of the season, because I need to rest. That’s the principle motive.
“The most important thing is we have three exciting months left in all three competitions. In one of them, we are in a difficult situation but if the stars align, we will have a chance to turn it around.”
Barca’s win over Sporting took them to the top of La Liga, one point clear of Real Madrid, who have a game in hand. They face Alaves in the Copa del Rey final on 27 May.
Former Spain midfielder Enrique featured for Barcelona between 1996 and his retirement from playing in 2004.
He then coached their B team from 2008 to 2011, returning to the club as first-team boss after spells managing Roma and Celta Vigo.
Former Barca coach Pep Guardiola paid tribute to his ex-Nou Camp team-mate.
“I have two reactions, as a supporter,” Guardiola said after his Manchester City side’s 5-1 FA Cup win over Huddersfield.
“I am sorry it is the club of my heart. I am so sad because we will miss the perfect trainer for Barcelona, from his personality and his character.
“His three years he played unbelievable football, with unbelievable players. I am like a fan with a membership of Barcelona. I can say thank you for all he has done in his three years at my club.”
Club president Josep Maria Bartomeu said: “Luis Enrique has brought us great success and he can still bring us more. The players are motivated to do it.
“We accept Luis Enrique’s decision. He has been a great coach. Now it is time to end his spell in the best possible way.”
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