Response to what is significant self sacrifice obligatory

When is significant self sacrifice obligatory?

One day, I happened to donate a small sum of money at a cash register for a particular then active charity.

No sooner had I walked out of the grocery with stores in tote, then having in the parking lot crossed a sum of the same amount on the ground.

There could be many interpretations of this I imagined.

To this extent, I remember having read in another context someone having said to the effect of another's charity: why do or give if you have animosity doing so?
Transcending a bit the abstracts of passion to social justice, there is something of a personal statement concerning direct involvement in active charitable work, and maybe this is very true: what help could you be to yourself and others, if having eroded the charity that you sought to provide?  Is 'sacrifice' an obligation as in duty, as in not having some other desired life relative to another path 'sacrificially' chosen?

Returning to the abstract,
As to the effect of charity,  it seems behaviour is much complex here.  What profit might be had of charity that could be utilised in so many ways?  Much in line with the article above, it seems that even in the efforts of organisations themselves, however, large, diverse, and responsive to any number of circumstances are neither entirely holistic to condition of any and every plight when it has arisen.   How much time and attention should be devoted?  Maybe some consider any effort enough, while others would claim so much could be done significantly reduce or remove a condition in a society?  And if resources are finite and limited what suitable balance should exist in so far as donation of time and monies?

When any number of problems have emerged or have existed simultaneously, how are resources used in addressing these?  Does any one charity resource sufficiently provide address to all?  And how does one intelligently make decision as to what priority in addressing should exist?  Maybe obligatory and thoughtless donations could be ill served?