There is only so much that your nervous system can take at any one time. And, everyone is different. For example, my hearing is very sensitive. I hear things that my husband can't hear. It's always been that way. So, if we go into a crowded restaurant with everyone talking, he will say to me, "we have to leave, right?" It's too much for me. Period.
You may be someone who can't take bright lights and wear sunglasses and a hat when you go outside. Someone else has trouble being with a lot of people at once. Most of us are troubled by negativity.
The main point is to learn what too much means to you. It could be too much of people, places, things, energy, words, news, certain sounds, etc. This is a personal awareness. Too often, you may find yourself forcing a situation when you know it isn't good for you physically, mentally, emotionally and/or spiritually.
Once you are able to determine what too much looks and feels like (which does take practice), it's time for Plan B. What can you do to re-balance your energy? As you know, there will be times when you get into overwhelm. Life happens. What works for you? Do you need to go for a run, go to bed early, have a healthy dinner, journal, take a walk in nature, hang out with your dog, leave a relationship, take a flower essence, use an essential oil, look a baby billy goat videos? It has to work for you.
Practice being aware of what your body tells you in different situations. Try various techniques for re-balancing your energy. Keep it simple.