Jon Hamm's romantic partner of nearly two decades, Jennifer Westfeldt, supposedly decided to end their relationship because his partying got to be too much for her to bear.<br />The 44-year-old Mad Men star dated writer-director Jennifer for 18 years until they confirmed their relationship was over on Monday.<br />"Jon and Jennifer really fought hard to make their relationship work, Jennifer more so than Jon," a source told ET Online.<br />"They were together for many years, but in the end, it was too much work.<br />It's no secret that Jon likes to go out and leads a very party-heavy lifestyle.<br />And Jennifer was just tired of that.<br />"She wanted him to grow up ... and he never wanted to.<br />She was tired of being his mother."
