Replacing selfishness with the right knowledge
Selfishness is conceptual nervous energy existing in the mind, and this concept is totally wrong. A wrong concept can be removed only by a right concept just like a diamond can be cut only by another diamond. Of course, while cutting a diamond, not only is another diamond required but even the process of cutting needs to be forceful enough.
The other diamond in this case is knowledge and the force in the process of cutting is devotion. Therefore, the right concept associated with devotion to God succeeds in destroying selfishness. When selfishness is cut at the root, your service to God will be perfect and will please God.
Service to God with selfishness will not fetch you the real grace from God. You can only receive some boons to satisfy your selfishness. In fact, selfishness grows more and more by attaining boons just like fire grows more and more by receiving fuel; the process of pacification of selfishness only increases it more and more. You can never subside selfishness by such a process of pacification.
Selfishness really subsides when it is cut by knowledge associated with devotion. Your service to God without selfishness then will fetch you the real and immense grace from the God.