Jahanbakhsh joined Feyenoord from English Premier League team Brighton due to lack of playing team.
The Iranian winger scored just four goals in 27 matches for the Eredivisie side.
“I know it wasn't good enough,” he said in an interview with ESPN.
Jahanbakhsh wants to prove himself this season. Last year he came to De Kuip with high expectations, but he was worse than predicted.
“Last year I missed a big part of the preparation. Now I'm there from day one and that's important. It's good to build it up,” he said.
“I know it wasn't good enough last season. I expect a lot from myself. Last season, I played good games sometimes, but I expected more from myself. I hope to keep my confidence,” he concluded.