A rushed morning sets a reactive tone for the rest of the day, while even a modestly slower start tends to carry a calmer baseline forward - the effect is disproportionate to how much extra time is actually involved.
A slower morning doesn't require an elaborate routine to be effective - just fifteen minutes of buffer, used for anything unhurried, produces a noticeably different start than a morning with zero slack built in.
Deciding what to wear or what to eat the night before removes a small but real source of morning friction - fewer decisions required at a groggy hour means a calmer transition into the day.
Checking messages and notifications immediately upon waking sets a reactive tone before the day has even properly started - delaying that check by even a short while preserves a calmer opening to the morning.