There’s no reason to believe that all is good when nothing seems very good at all. If you try to believe that all is good when things seem bad, then you may feel like you’re missing out on everything. When there is so much suffering in the world, it is absurd to think that all is good. Yet all is good.
Even when things seem bad, that badness is contained in goodness. When things feel good, that goodness is contained in badness. Neither good or bad is absolute, they are what we make of them. Because good and bad are relative to us, we have the power to change them or change ourselves in relation to good and bad.
The possibility that we have power over good and bad is ultimately good. That we are not sure how to exercise that power does not diminish the power. Entertaining the possibility that all is ultimately good helps us to look for goodness amidst the badness, which helps us to exercise our power over good and bad. If this practice reduces our suffering or the suffering of others, that is good. If we are able to transcend our suffering, transcend good and bad, then it no longer matters if all is good. All just is.