Buddhism makes much of 'impermanence'. This has several to it.
1. These teachings tell us that all the conditions that we meet within samsara are fragile. Whatever circumstances we may build our expectations upon, they can never be wholly relied upon. Simply recognising this can lead us to be more 'philosophical' when things do not work out as we expect. You might campaign for one thing and the other eventuates - are you going to mope, or grasp the nettle?
2. The Buddha saw beings 'rising and falling according to their deeds'. Sometimes people seem to be doing well, yet are unhappy inside. Sometimes others seem to be doing badly, yet have inner strength. It is difficult to tell the inner story. As conditions unfold over time each person is tested and the quality of their life bears fruit. Sometimes one gets one's comeuppance. We can have sympathy.
3. Teachings on impermanence also impart urgency. Time is short. We only have this human body for a brief period. It is no use waiting for life to begin or the right conditions to show up. This is it. If we are going to have a meaningful life, this is the time to get on with it.
4. Whatever disaster befalls, whatever terrible circumstance arises, it will pass. A storm rarely lasts all day. Therefore we should cultivate patience. Don't get caught up in ignoble words and deeds that are but the froth of the moment. Take a longer term view.
5. Impermanence offers no permanent succour. While engaging with impermanent conditions, it is also important to seek a more reliable refuge. Not everything is impermanent. Buddhism orients us to nirvana. By having faith that transcends the impermanent world we find the core of the Dharma.
These five points, to be philosophical, to have sympathy, to not waste time, to be patient and to seek a true refuge go the the heart of the matter.