You might conceive of your whole life as one vast project, but if you did, when would you reflect on the project's hopeful success? It would be crazy only to do so on the last day of your life as, for a start, who knows when this might come? Surely it makes more sense to consider this one overall 'project' as being built up of many smaller packages, and to look back frequently at how you've done.
Being more aware of the ups and downs of your mood means that when things go well, you'll have the reward of seeing how you are holding up. Alternatively if you're not having such a great time you'll gain the insight necessary to take action, ideally before things become overly low. In general I'm sure it makes sense to live your life day by day, reflecting often on how things have gone and what you might do to maintain a positive state of mind. What can you do today that might make you feel better tomorrow?