Battery aging is real: lithium-ion batteries hold less charge as they cycle. But daily drain is often dominated by a few predictable settings.
Brightness is the classic culprit. If your screen is pushing max brightness indoors, you are paying for it in hours.
What usually drains it first
Another hidden drain is background activity: apps refreshing, syncing, tracking location, and sending push notifications. Each one is small; together they add up.
Heat matters too. Charging under a pillow, in a hot car, or while gaming heats the battery, and heat accelerates wear.
What helps (without obsession)
Practical fixes: use auto-brightness, review app battery usage, limit unnecessary background refresh, and avoid charging in hot environments.
You do not need to panic about charging to 100% sometimes. Just avoid living at the extremes—very hot, very low, very full—for long periods.