I don’t really leave the house that often, mostly to walk the dog, but I don’t then cuz it’s a huge open air space.
I do on the bus because of how confined it is and how many people use/touch it, but besides that I have no idea.
Do you always have to wear a mask in these places? Or just when there is a covid spike?
How do you even know when there is a covid spike for that matter?
Covid can hang in the air like smoke, so basically any public indoor space, and any busy outdoor space. One sick person shedding virus, whether they present as sick or not, can fumigate a small area with covid for a while. It's best to assume there's covid around even when cases are low.
A small room with a few people? I don't worry about it that much outside of covid peaks, personally, but it kinda depends on how much you trust them to not lie about symptoms or recently being around someone sick.
If peer pressure or malaise of not doing stuff gets the best of you (this happened to a few people I know who are otherwise pretty covid aware still), at the very least look into nasal sprays like betadine.
What do nasal sprays do?
They typically coat your nasal passage in with stuff that makes it hard for virus/allergens to survive. Betadine has something called iota-carageenen, which comes from seaweed, and it envelops small particles like a virus before it interact with your nasal passage and infect you. Other sprays have different formulas and do slightly different things, but essentially attempt the same type of thing. Betadine helps my allergies so in my experience I can tell it's intercepting allergens at the very least.
Not foolproof, and not a good sub for masks, but it helps your odds a bit.
And one of the ways covid can enter your brain is through the olfactory bulb in your nose, which is why so many people have long term problems with smell, so protecting that is probably a good idea.