You’re only worried about fresh breath in the morning
Because we haven't eaten yet, we assume the morning brush is less important. Hey, you brushed after last night's dinner, that's good enough, right? Wrong. During the night, a combination of not drinking and not eating alongside consistent airflow make for a germ-growing environment that becomes exponentially more friendly toward decay-causing bacteria. So give your morning brush the same attention as any other.
You’re using bristles that are too firm (or too soft)
Brush heads are important because their arrangement, stiffness, and bristle density have all been optimized to clean your teeth in very specific ways. If you’re using hard bristles and have sensitive teeth, that’s not good. In general, flatly arranged bristles are best for overall cleaning, but bristles that form a stuck-out point on the tip are good for cleaning gum pockets.