Rough nights and a flat mood are a known, temporary part of cutting nicotine down — chemistry recalibrating, not a verdict on how your quit is going.
Nicotine affects the same brain chemistry that regulates sleep, so cutting down can mean a rougher night or two — vivid dreams, waking earlier, trouble settling. It's a known, temporary part of the adjustment, and it typically eases within a week or so.
Source: NHS — quit smoking timeline
Feeling irritable, flat, or on edge while your intake drops is a chemical adjustment, not a sign anything's wrong with you or your quit. It passes as your body recalibrates — it isn't a verdict on how well you're doing.
Source: NHS — quit smoking timeline