Compassion can be roughly defined in terms of a state of mind that is non violent, non harming and non aggressive. It is a mental attitude based on the wish for others to be free of their suffering and is associated with a sense of commitment, responsibility and respect towards others.
In discussing the definition of compassion, the Tibetan word tse-wa, there is also a sense to the word of its being a state of mind that can include a wish for good things for oneself.
In developing compassion, perhaps one could begin with the wish that oneself be free of suffering, and then take that natural feeling towards oneself and cultivate it, enhance it, and extend it out to include and embrace others.
The 14th Dalai Lama.