Boddhisatvas and saints are happy, they experience great joy and peace. But they also have a constant awareness of suffering. The condition of life involves existing in a constant flux of suffering. When suffering temporarily dips lower we call that happiness and when it temporarily goes up we call that suffering. In Buddhist terms, this is the product of the attachment system. In terms of the Desert Fathers we could call this the product of demons. However, there is a source of true happiness and peace that everyone has access to. It is always there but it is obscured by our constant focus on the ups and downs of suffering. In Buddhist terms, this is Buddha nature. Christians might refer to this as a connection to God. To experience it we need to clear our minds of the goals and conditions that drive the attachment system. When we fail to do this we experience a different type of suffering, one characterized by the absence of Buddha nature or God's presence. However, people who have had little experience with this experience do not miss it as much because they are unaware of what they are missing.
Bodhisattvas and saints are constantly immersing themselves in suffering. In particular, compassion causes them to focus on the suffering of others and desire to alleviate it. And yet they are happy, joyful, and peaceful. This is because they understand the true nature of suffering and do not get caught up in trying to escape it. By doing so they use their attachment system only sparingly, allowing them to experience nirvana or grace.