Justin Timberlake was struggling with a "debilitating" medical condition throughout the entirety of his Forget Tomorrow World Tour, which wrapped in Istanbul, Turkey, on July 30.

The "Suit & Tie" sensation shared a lengthy message on Instagram to mark the conclusion of the tour, referring to it as "the most fun, emotional, gratifying, physically demanding, and, at times, grueling experience." He explained that he gave "all that I have to this. I could not have done it without my family, friends, the TN Kids, and all of YOUR support."

The star also revealed that he endured a "mentally and physically" exhausting battle that fans were not privy to.

"I’m a pretty private person. But as I’m reflecting on the tour and festival tour – I want to tell you a little bit about what's going on with me," he began.

"I’ve been battling some health issues, and was diagnosed with Lyme disease — which I don’t say so you feel bad for me –– but to shed some light on what I’ve been up against behind the scenes. If you’ve experienced this disease or know someone who has — then you’re aware: living with this can be relentlessly debilitating, both mentally and physically. When I first got the diagnosis, I was shocked for sure. But, at least I could understand why I would be onstage and in a massive amount of nerve pain or, just feeling crazy fatigue or sickness. I was faced with a personal decision. Stop touring? Or, keep going and figure it out. I decided the joy that performing brings me far outweighs the fleeting stress my body was feeling. I’m so glad I kept going."

For more, read Jessica Biel Shares Rare Glimpse Of Her & Justin Timberlake's Kids, and check out Timberlake's full message (including a carousel of unforgettable tour memories) below.

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Jana