What an important and difficult question...There are at least two things here which I'll separate in my reply:
1. How to deal with misery?
2. How to deal with excess?
Some remarks about the first: I think one has to remain aware of suffering in the world just as you would keep your eyes
open to any other aspect of existence. It it always useful, as much as
one can, to look at the world clearly just as it is, to not pretend
things aren't there but to acknowledge them and remember them so that
one can act as correctly as possible, without sentimentality or fear.
Educate yourself by talking to people who work in charity and in
humanitarian organizations or political action groups so that you can
make sure as much as possible that your day to day life does not
unwittingly undermine your principles -- e.g. do basic research to see whether things have been produced in sweatshops, buy from companies whose politics you find reasonable, etc. Read about the particular social and economic problems in your own city or region and, insofar as possible, support local groups which try to deal productively with the roots of the problems.
Some remarks about about the second:
You mention the "semi-constant anxiety" of having while others do not, or of not stopping everything you are doing to help each person you see. I can very much relate to this and I think that for many of us, women especially, there is often a kind of guilt involved in living which one has to be very careful to avoid. This is a subtle thing, because obviously in small amounts it is simply sensitivity to others. But in a deep level one also has to feel that one can give oneself the necessities of life, allow oneself a certain pleasure, and not constantly apologize for one's existence; because in a deep sense, not
giving oneself the necessary resources to fully develop one's potential is fundamental selfishness, and deprives the world of something potentially much larger and greater. I don't mean that you should buy Gucci bags with abandon, but if by occasionally taking wasteful bubble baths and buying reasonably nice clothes and eating meat you free yourself to delight in life and devote your energy to your work, as a result of which you are able to run for local government and personally oversee the development of a microcredit agency to give thousands of poor women a livelihood --- well, then that's more than a fair trade. Mia's been quoting Emerson
, who says elsewhere in Nature that
The true charity of Goethe is to be inferred from the account he gave
Dr. Eckermann, of the way in which he had spent his fortune. “Each
bon-mot of mine has cost a purse of gold. Half a million of my own
money, the fortune I inherited, my salary, and the large income derived
from my writings for fifty years back, have been expended to instruct
me in what I now know
This also resonates, I think, with what Edna has written. Be open to ways that your own particular gifts in the world can be used for creative problem-solving, but don't be afraid to privilege your own long-term self-development over what might seem like short-term waste, again while acting as ethically as possible.
Looking forwards to others' thoughts --