15 hours a week training on my bike broken out as:

6 hours riding on my own, a mix of shorter intervals, 2x20s, hill climbs and other training
4 hours fast paced group riding
2 hours of training crit
3 hours of road racing or if no racing 3 hours of riding on my own

I was also hiking between 7-10 hours a week.

The biggest thing was that I was riding every single day and keeping the above schedule for months on end. Almost every ride had a lot of really hard efforts. I bought into the myth of the "recovery ride" and just didn't think I needed to stop riding like that. It was also an outlet for difficult working situation so there was additional motivation to ride every day as it was a strong coping mechanism. All I did was ride, eat, sleep and work. Definitely a mental health component but its harder to figure that part out.

Like I mentioned above, everything was going really well until it wasn't. The signs were there but it was easy to ignore them as I was getting faster until "all the sudden" I wasn't.