I've been thinking these days, sometimes we underestimate the feelings of others below ours, it is true that we must protect ourselves and value ourselves but sometimes when we go beyond that, we do not only "protect" ourselves, sometimes we go beyond the limits of tolerance of others and we can reach or ignore their emotions and feelings or worst hurt them, just because we only think about us.
Sometimes, in discussions, in situations of stress we forget that there are other people around us and just because we want to defend ourselves we can become blind to the feeling or the thoughts of the other people, and it is not until much later, or even when it is too late when we realise the damage we caused, and I wonder why, the answer is very easy, SELFISHNESS, selfishness of ourselves, when we lock ourselves and put a wall and believe that only we and our feelings are the ones that matter and it's not like that at all, we have to know how to lower our guard and understand that just as we feel, others also feel, as something bothers us, displeases us or hurts us, others too, not only we matter, we all matter and we all feel the same.
We have to learn to be empathetic, to feel both the joys and sorrows of others, because we do not know what kind of storm each person carries inside, because maybe one day, we will be on the other side and the ones who need the other person to feel like us and lower the guard. One day can be YOU.
There's a lot more to it IMO. Some just "give but can't take it", some are so triggered that anything hurts their feelings. But you are right in the fact that one should consider those around. Once you have said something hurtful you can't take it back. "You can't unring the bell".