The NY Times has an article ("The Pathological Altruist Gives Till Someone Hurts") that discusses how too much altruism can become harmful. The article contains items from a a book that will appear in November of this year.
This harm can concern the receiver. The article gives the example of an oncologist who kept on treating a patient for whom there clearly was no hope - despite the fact that the treatment was very painful.
One way to sacrifice oneself is for a group with a cause like a religion or a political party.
Another was is to tolerate a lot from other people like the spouses from alcoholics, other addicts or abusive partners do.
Yet another way is to be desireless like the article discusses for anorexics: “They try to hide their needs or deny their needs or pretend their needs don’t exist,” Dr. Bachner-Melman went on. “They barely feel they have the right to exist themselves.” They apologize for themselves, for the hated, hollow self, by giving, ceaselessly giving.
At the end the article discusses a very special form of "altruism": people who keep large numbers of dogs, cats or other animals. This may be too much for them and result in neglect of those animals. Yet they don't see that and instead feel happy about being needed by all those animals.