Personally for me it was motivation when I couldnt fly.For various reasons weather, serviceability, sickness if you start getting delays in your training its pretty frustrating.
For me this occured due to various reasons and I started to get increasingly frustrated with my lack of progress due to events outside of my control.
It was a like a snowball and I started getting more and more uptight, in turn getting more and more tense. Didnt do me any good at all. I was told that I shouldnt worry about my rate of training and that it wouldnt affect my progresson the IR, something I personally feel is that's open to debate.
So try and stay calm in it and take what gets thrown at you. easier said than done.
FS