Highly sensitive and introverted people create their own energy. This is an important thing to recognise and embrace. It's also important to recognise that if you’re responsible for managing and creating it then external sources can potentially take it.
This is a key difference between extroversion and introversion. Introverted people get their charge from being away from stimulation and people, whereas extroverted people may find that they draw charge from being around other people and doing highly stimulating activities.
Remember to Turn the Power On
It's not enough to simply step back from the world. There are times when I am alone but not re-charging. In an interview I did with Kaitlyn Mirison she described this as 'numbing out' and it's just as bad for us as being overwhelmed and over-stimulated.
Protect your resources and embrace limits.