There are a lot of people trying to do “lean startup” or “lean UX” and fretting about whether they are doing pure lean (there are even more who talk about lean but don’t actually do anything close, but that’s a different story).
There is no such thing as pure lean. The right balance takes into account what you need to accomplish and learn, but also your context and constraints.
What you shouldn’t feel, in my opinion, is a need to be learning every second, or a need to test everything. You’ll end up being way too inefficient.
And when you do focus on the important things, I suspect that you’ll find that lean feels a bit like a sine wave.
You create an experiment and learn. Then your learning curve starts to flatten. You need to absorb and interpret your data. You need to make decisions and put your decisions into action. And then at that point you are ready to start a learning cycle again. Out of the building, then inside the building, then outside again. Learn, build, measure, learn, rinse repeat.