I started doing the WOD at the beginning of January. There are thing that I can do and things that I can't (yet). I try to stick with the exercises as Rx'd, but I know myself well enough to know what I have to scale. With this, I have been able to do almost every WOD since I started. After the initial soreness wore off, I began pushing myself as hard as I could, particularly on strength excercises. Even where I scale things, pull-ups for example (I use a green jump stretch band), I go as hard as I can. Another example, knees to elbows. Not a chance! I sub sit ups and leg raises. I try to push my limits as often as I can, but I balance that with the benefits of doing the WOD consistently 3 on 1 off.
The other thing to consider is nutrition. Make sure you are getting the proper amount of each macronutrient at each meal and eating the correct number of meals. I am a zone guy (as are many others on this board) and I believe it works. I rarely get tired anymore and I recover well from most workouts. This may be something you want to consider. Keep at it. It's worth the effort.