I am definitely not a polished person - on holiday or at home - but these things help.
I always have a haircut (I have thick wavy hair so go a lot shorter in summer) and get my nails and feet done the day before I go.
Lots of moisturiser, twice a day.
Never bother with make up during the day and if hot in the evening just light eye make up and lip gloss.
After a lot of mistakes with over packing to work around a few anchor items. For city breaks in cooler months jeans and a denim skirt then more intetesting tops. For hot holidays then plain tops that go with most clothes and more interesting print skirts, dresses and bottoms. Skirts and dresses in light cotton jersy are great as they pack well (can be rolled).
For hot holidays Uniqlo airism under vests are a revelation, they help tops sit better and absorb any sweat.
When out and about on hot holidays I always carry tissues, hand santiser, vaseline (great for when sandals and bra straps rub) water, a large light cotton scarf and a light scented cologne to spritz (I like the ones Korres do).