For quite a long period of my life, from middle school through post-college, I was very serious about trying to be a good runner. I ran track and cross country and had gotten to the point where I was often running 90-100 miles a week in order to try and get stronger and faster. I'd structured quite a lot of my life around being able to fit in that training and racing. I had a few setbacks all in a row, an injury, a bout of overtraining, etc., and basically started to see that I simply didn't have the motivation to keep up all the long hours of training when I felt like I was seeing diminishing returns.
In the end, I did replace racing and being competitive on the track with trying to learn to race a bicycle as it provided a new outlet and one where I could actually get better instead of just prolonging the decline. So in my case I replaced the outlet for my competitive desire but didn't really change the habit or attitude.