Struggling to keep walls straight when building with lumber

Haha, "gentle ocean waves"—that's a perfect description. I'm about halfway through my first custom build right now, and I almost skipped acclimating too. Luckily, my neighbor caught me unloading lumber and gave me a friendly heads-up (plus a horror story about his own wavy walls). Glad I listened... walls are straight so far, fingers crossed. Definitely one of those steps that's easy to underestimate until you see the results firsthand.