I Feel That Something Is Missing From My Life

It's very strange. I work hard and enjoy my hobbies such as practicing guitar and learning Swedish, and speak with my friends, yet I still feel something is missing in my life and I just can't put my finger on it. I know I have everything I could ever want. My life is simple yet full of joy and love. I told a friend this issue and she said that I am overthinking and overworking myself with this belief and that I should just relax. I make sure to get plenty of that and have a healthy sleep schedule. I workout and eat well, and I smile and laugh with others. But still I feel this odd emptiness in my chest every now and then. Something is missing. I tell myself I have all I ever need, to live in the present, that I never know what I have until it is gone. Yet why do I still feel this way? It is very perplexing.