A suit comes into its own in that run of weeks when your diary fills up with things you can't wing in a jumper and trainers, an interview, a funeral, a work presentation to people who outrank you, a stretch of back to back days where you need to look like you've got it together even if you absolutely haven't. That's when it matters, not on a random Tuesday when a dress would do just as well and feel a lot less like armour.
It is the wrong choice for anything that needs you to move properly, a long day on your feet, a journey with bags, an evening where dancing is on the cards, because even a soft jacket restricts your shoulders in a way a dress or separates simply don't. Buy the jacket and trousers apart if the range allows it, because almost nobody is the same size top and bottom, and a jacket that fits your shoulders but gapes at the waist looks worse than one that's slightly off everywhere at once. Sit down properly in the trousers before you commit, a real sit, not a perch on the edge of a changing room stool, because the ones that look sleek standing up can pull tight across the front or ride up at the ankle the moment you bend. Sleeve length catches more women out than it should, a cuff that swallows your hand reads as borrowed rather than relaxed, so get it taken up even if that feels like an extra errand for a high street buy.
Keep the rest of the outfit quiet around it. A heavily patterned top or a statement bag turns a suit into a costume rather than an outfit, and the same goes for trainers that are trying too hard, a clean pair works, a scuffed pair reads as an afterthought. It sits best from early autumn through the depths of winter, when a bit of weight in the cloth feels right instead of stifling, and it covers interviews, client meetings, funerals, the odd smart wedding where a dress feels wrong for the room, and any day you want people to stop quietly checking whether you're actually in charge. Worn stiff straight off the hanger it can feel like you're wearing someone else's confidence, worn in, with the shoulders softened and the knees of the trousers a little broken, it stops looking like a costume and starts looking like how you just dress. I'd rather own one good one than three indifferent ones.