Atletico are a point clear after Sunday's win at Barcelona.
De Paul said, "When you suffer the most, you also enjoy it the most. We faced a great rival. We were playing for the lead. There were many things at stake. We have been working very hard. This is only the result of hard work. It is well deserved that the team closes the year like this.
"To play this type of match you have to be prepared to play and also to suffer. We were up against a very good opponent. I am very happy for the whole team."
He added: "Obviously there is excitement because we are at the top. Satisfaction when work and effort bear fruit. My daughter asks me to celebrate and I do it.
"I'm very happy to be at Atlético. It's an honour to wear this shirt. When things go well, it makes me happy. I hope people are already celebrating in Madrid."