The point to be understood is that if we work for the welfare of others, then our own goals, our own wishes will be fulfilled naturally. When we think about it, the welfare of others is important because others are important. They are important because they help to fulfil our own wishes. A mundane example is that if we had a wish to become wealthy, then we have to rely on someone else who has wealth so that we can earn from them. Whatever we wish for is all dependent on others; others who have the means or qualities that can fulfil our wishes. There is no way to gain anything for ourselves without relying on others.