Some anticipate a benevolently-orchestrated afterlife will compensate for selflessness in this life. 72 virgins, stuff like that.
As for me, I believe most suffering is the inexorable result of overpopulation to "life is cheap" levels, which there's no ethical way to fix within the lifetime of today's generations. I'm willing to pay my fair share (not more) out of our society's resources to treat the symptoms, but I'm not going to divert my own efforts and sacrifice limited opportunities for the rare experiences I value most.
I hope you will reconsider that belief about overpopulation, because its completely incorrect and racially and/or class based. Do the Greeks have 40% (or anyway a very high number, don't know for sure) unemployment because they are overpopulated? What about Somalia, is that country overpopulated?
The United States uses more oil than the other 3 or 4 top countries combined. The reason there is so much suffering is because resources are not only distributed incredibly unfairly, but actually many countries and groups are deliberately repressed.
If Greece can sufficiently exploit its resource base with just 60% of its population, yes, there are far more Greeks than they need, and the rest are being ill-treated because their presence is seen as a burden rather than an asset. And wasn't Somalia officially in famine just a month ago?
On reflection, I shouldn't have said "no ethical way to fix". A fundamentally different civilization, freed from our punitive "if anyone will not work, neither shall they eat" attitude, needn't make people suffer for being regarded as superfluous by the economy. And defense against "why should we feed you?" is largely why societies lacking trusted safety nets do overbreed whatever resource base is available, including foreign donations.
As for me, I believe most suffering is the inexorable result of overpopulation to "life is cheap" levels, which there's no ethical way to fix within the lifetime of today's generations. I'm willing to pay my fair share (not more) out of our society's resources to treat the symptoms, but I'm not going to divert my own efforts and sacrifice limited opportunities for the rare experiences I value most.