What does “feeling flat” mean. Does that mean “meh, I don’t really wanna go to the gym I’d rather curl up under the blankets and read a book” or does it mean that you feel wrecked. Like you feel like you’re starting to get sick or sore or like you couldn’t do the work out if you wanted to.
I know when I first started it was hard to get used to getting home from work and turning around out the door every night even when I felt like chilling and reading a book. And it was hard again when I started doing morning runs (lol its still hard). But that is different than feeling like you’re starting to get sick or over worked. One is motivation and one is over training.
Also, you’re supposed to start at 50% of last year, I wouldn’t count lunch time “strolls” as a workout, so I would assume you were at 3-5 hours per week assuming you were running or climbing 3-4 days per week (Because if you think about it, 2 hours at the climbing gym is probably only 30-45 min of actual on the wall climbing). So maybe you should be starting at 2-2.5 hours per week? It seems like a very small amount of training but it basically grows exponentially and by the middle of the base period you’ll be doing huge volumes (comparatively).
And finally, you say you eat healthy, that means a lot of things to different people. One thing that I find helpful is to track food using something like my fitness pal and after getting a baseline of what you eat normally, try tweaking things and keeping track of how I felt vs how much I ate. So get a baseline for 2 weeks and then try upping fat or upping protein or upping carbs. There is a lot of research on what the balance of macros should be for muscle building or fat adapting or recovering.
Anyways, good luck, its more of an art than a science it seems. Its taken me until midway through my max strength period to feel like I really have a handle on everything. 🙂