Breakdown Cover. The squirty stuff is in the boot, but never used it before so no idea if it works or how effective it is.
I think I've had 3 flat tyres in 15+ years of driving. One of those I had to call the AA out anyway because the idiot I bought the car from had changed the wheels but not the wrench and it didn't fit, and the idiot who owned it (me) hadn't bothered to check when buying it - it also only happened because the tyres were far too old, which again I hadn't bothered to check. Of the other two, one was fine to drive round the corner to get a new tyre (also a very cheap and probably old tyre on a very cheap ebay car), and the other one was the only occasion when a spare wheel has come in handy but, I probably would have been fine driving that 1 mile to the garage as well.
So in 15 years that's probably one flat tyre that couldn't have been prevented by having tyres in good condition. I'm ok with having to get the AA to tow me to a garage once every 15 years.
Squirty stuff + AA cover = nothing to worry about.