The above quotation comes from the inestimable C.S. Lewis, of which, this pithy advice, serves notice that as much as mankind spends an inordinate amount of time trying to find happiness in all sorts of activities, escapes, selfishness, and ego fulfillment -- that mankind as long as it stays upon these diversionary routes, will invariably find itself actually getting further and further away from the true path of happiness. While there is much of merit here on this earth, and much to do to make it better, there are also plenty of sideshows and wrong actions that mankind has shown way too much of an inclination to devote time and resources to, only to find out at the very last hour, that all of this has be in vain, and for nothing much more than temporal vanity.
Those that insist upon substitutes will invariably lead lives of which that substitute no matter how enticing it may at first seem, will never be able to fulfill their true heart's desire, for that substitute does not have and never will have the means to satisfy anyone, fully. This signifies that all those misguided people that spend time doing that which will not bring them that type of lasting joy and satisfaction of a good mission, well done, are going to invariably be disappointed; though they may, for a time, find some joy and satisfaction from that activity, but, of which, it will not and cannot last.
It is amazing, that many a person that refuses to accept that which is fraudulent and/or of inferior quality as being just as good as the real thing in their material interactions, somehow yet believes that the pursuit of that which cannot ever end well, will somehow end well, when that cannot be. It isn't that we are meant to simply worship God night and day, as if that, alone, will make us happy; but rather it is imperative that the thoughts, actions, and deeds that we do throughout our interactions with others that are part of our community that we are in, are consistent to the attributes of what makes for justice, compassion, fairness, and wisdom.
Those that are most satisfied and thereby happy, are all those that have aligned themselves to the best of their ability by their thoughts and by their subsequent actions so as to synchronize with that which is the Creator of it all. If we truly want what is best for ourselves as well as for others, so as to have that inner peace of knowing that we are doing right, then we need to take to heart the wisdom of the ages, and that wisdom will not ever steer us wrong.
The failure of mankind is the repeated failure of mankind through its sustained belief that somehow its individual self-serving wisdom is the superior wisdom, which should be adhered to by all others, and that those that will not listen and obey, need to be taught to obey. That corrupt mindset is the very basis for all that is wrong in this world. Rather, that which mankind needs in order to find that inner peace, is that which mankind needs to freely avail itself of, and when mankind finds that which must be found, then that which is false and disappointing will be replaced by that which is True and ever satisfying.