My bank has free bill pay, so my wife and I have an automatic check sent out every month to a local all-volunteer charity that does very worthwhile work. We never see that money and we budget around the income we have left over. Whenever I peek at my bank statements and see those debits, I'm reminded of what we're doing.
Even a small amount, say $50/month, is a great start. This also forces you to find a worthwhile cause now, and to attach yourself to and actively re-evaluate that cause on an ongoing basis. It becomes a part of your life instead of your future.
All that said, thanks for the honest discussion. This stuff is important.