A sense of accomplishment, belonging and inner peace needs to come from realization of self awareness and self worth rather than from achieving future, external goals.
We feel empty not because we have yet to achieve a goal that society sets for us in order to feel content but because we are not alright with ourselves. We may feel weak, ugly, stupid, and generally inferior. All such concepts gather and form the idea that we aren't worth loving or worthy to exist or just that life is meaningless.
We get to this state as individuals and seek validation from external sources like significant others, occupations, social status. We think once we achieve these things then we can finally be allowed happiness. But living like this is the act of trying to extract life/worth from things around you rather than realizing and harmonizing with the life/worth within yourself.
We need to sit in quiet and truly ask ourselves, not society, "what is it that I want deep inside?". If the answer is specific, like a job title or fame, we need to ask ourselves again "why do I want this thing?". And again and again. Eventually we get down to base emotions. We start to identify the emptinesses within ourselves that make us so discontented with life. We find what we've been running from.
We need to realize and see for ourselves, not just have it told to us by others, that we are indeed beautiful, worth loving and worthy to exist, even if it seems no one else thinks so at times. Once we start to appreciate and start living for ourselves in the present, not for future goals, we can begin finding happiness and contentment in every passing moment. The world begins to look different and we can begin to see the beauty in even simple things again as we used to as children. A child doesn't place their happiness on distance future goals but seeks it out from every passing second and actively lives it. That is the mindset that adulthood steals from us but it is a far truer way to live.
It took me a long time to realize this. Society doesn't teach us to think this way. Society tells us to fall in line and if we meet its standards then we can earn our happiness. Pensive self reflection is a lost art in our lost world but it is an essential spiritual awareness for being content and finding our place.