NO is seen as such a negative word but it is all about perception. Saying no can be seen as selfish, but often saying yes is actually the worse option. Saying yes and then not being able to give the best version of you, giving low-quality time or effort is much more upsetting than saying no.
You can do anything, but not everything!
Saying yes all of the time can also leave you feeling tired, stressed and overstretched which often causes you to become run down, leading you to more susceptible to illness. Your immune system is your main defence system, and when you’re stressed this negatively impacts how well you can fight off bacteria, germs and viruses. This could in turn impact your prior commitments, possibly leading to you having to say no to much more important things. So before getting anxious about having to say no to someone, remember the chain that saying yes to one more thing could cause.