My cat hissed at me for the first time. Should I be worried?
Hissing occurs due to several reasons. It is a normal behavioural response.  Ensure your cat is well-fed and hydrated. Allow it to enjoy its own free time and space. If your cat gives off signs of exhaustion or overstimulation, stop engaging with it.  If the cat is continuously hissing due to no discernible reason or being aggressive, you should visit the vet to rule out underlying causes.