The fear is slowly fading, and I can replace it with a new word; progress.
The internet defines progress as "development towards an improved or more advanced condition". In my case, this condition is an advanced physical condition. Anyone in a sport, profession, or anything at all which has a quantifiable level of success; knows that a graph of progress is not linear.
Whilst this means that weeks and even months can pass without progress, it does also mean that there can be breakthrough moments, in which a large amount of progress is made in a short space of time.
I feel that this is an illusion; however, and that although it appears that you may have taken a large step forward, this is simply an accumulation of the hard work that has been put in, and it manifests itself at a certain moment in time for one reason or another.
My first proper track session last night was a moment of progress, culminating in the fastest set of 400m repetitions I've run since July. Although these are times I could run with relative ease last year, it is indeed progress after a period of time in which I felt none was coming.
Progress isn't owed to an athlete, it is earned by them, and they must respect the journey towards it, and not become disheartened when it is a slower or harder process than anticipated. My process is still in its early stages, but small signs of progress give me the inspiration to strive for more.