Results of Compassion
Rinpoche wrote the following to a university professor who was testing students after they meditated on compassion. Rinpoche commented on one of his questions about the nature of compassion.

My very dear Dr. Collins,
Thank you very much for your kind letter on the project.
I don't remember very clearly the previous questions you asked, but in this last letter there was one question that you asked which stayed in my mind. The question you asked was about whether compassion is sadness or not.
I would say that in the nature of compassion there is a feeling of something being unbearable, because of the suffering of others. Then, there is also a feeling of sadness because of other sentient beings’ sufferings.
If you analyze the nature of compassion, it is like that, but if you debate on the nature of compassion, then that might appear strange. If it is debated, it may appear strange to say whether Buddha has sadness or Buddha has unhappiness. For example, even though the texts do discuss how when you do wrong things then Buddha is displeased (displeased means unhappiness), that doesn't mean Buddha does not guide you or gives you up.
There is sadness due to attachment – when the object of attachment is lost, dies, the relationship ends, there are problems with the wife/husband, etc. The person who leaves his or her partner is very happy in some situations, if being together was suffering for him or her. By not being together, it is much better for him or her. But the other person, who was left, is sad and unhappy, because the object of attachment has left. Of course, that sadness is not compassion, that sadness and the nature of that sadness is unpleasant in nature. However, the compassion one feels when somebody is suffering, whether it is a relative or a stranger, that feeling of something being unbearable because the other person has pain or problems, that contains sadness, but it has a peaceful nature. That sadness is certainly different to the sadness due to attachment. The sadness from attachment has only a negative effect, whereas the sadness from compassion has only positive effects.
Of these two types of sadness, the one coming from attachment comes from only thinking about yourself, which is completely different to the sadness coming from compassion, which is thinking of other people and having a natural feeling that you want to help them.
I hope there will be some good results from your tests. I think the other most important thing that might happen is that many people will put more effort into the lamrim meditations, which will help them in the near future to have realizations of bodhicitta.
I hope you are very well and that in the future you will have time to come to Aptos to my house to relax a little bit and so we can chat more.
Sincerely with prayers,
Lama Zopa