Before How I Met Your Mother, she was in love with a man named Max. Tracy served as the mysterious "Mother" of the sitcom, and although details of her life were revealed throughout the series, the character didn't appear until season 8. The years leading up to Ted and Tracy's first encounter was documented through Future Ted's storytelling; his audience, of course, was the pair's two children.
Max was Tracy's serious boyfriend and, ultimately, her first love. The pair would have been dating around the time of the How I Met Your Mother pilot when Ted fell head over heels for Robin Scherbatsky (Cobie Smulders). By late 2012, Tracy began dating Louis (Louis Ferrigno Jr.), a guy she was with when she unknowingly met some of Ted's closest friends. Even though Louis ended up proposing to her, Tracy said no and eventually found Ted after meeting him at the Farhampton train station. The couple took the relationship slowly at first but marriage and kids were in their future.
The reason why Tracy rejected Louis' proposal was that she never moved on from Max. Rather than a typical breakup, Tracy's relationship with Max ended because he tragically ed away on her 21st birthday. She couldn't fully let go of Max and didn't start dating again until seven years after his death. Louis was the first person she dated following the tragic event, but her heart wasn't in the relationship. Even after dating Louis, Tracy held on to the ukulele that Max bought her prior to his death. Before meeting Ted, Tracy spiritually asked Max's permission to move on. The details surrounding Max's death were never revealed, but it was presumed to be a sudden incident since there was no indication of an illness. Tracy did have a chance to move on, though she poetically reunited with her first love by the end of the series.
Max Was Tracy's "Robin"
As explained in the How I Met Your Mother series finale, Tracy ed away six years before Ted began telling his kids about how he met their mother. Like Max, the details regarding her death were left ambiguous, but it was clear that she died from some type of illness. Following the end of Future Ted's story, his kids encouraged him to rekindle his romance with Robin. In many ways, Max was Tracy's version of Robin. Just like how Ted never fully let go of Robin, a woman he thought was "the one," Tracy never got over Max even though he was gone.
There was no doubt that Ted and Tracy loved one another and lived a happy life in their short time together. That said, Tracy returned to Max, the love of her life, mirroring the fact that Ted found his way back to Robin later in his life. Max never made a direct appearance on How I Met Your Mother, but he was an important piece of the puzzle when it came to the fates of the central characters.