Rumi said that there is an inherent sadness in the spirit of everyone. This sadness is caused by our separation from the source. We are deeply unhappy about being separated from the source. We cannot reach true happiness if we cannot connect with the source ( whole, Universal intelligence).
One of the core philosophies of Rumi or Sufism is the desire to return to the source. This separation of loneliness creates fear, anxiety, and insecurity. The true sense of happiness and wisdom is in joining with the source.
For this reason, Rumi started the Masnavi with the Reed poem which is the cry of separation. We are not secure and safe when we are separated from the source like a drop of water separated from the ocean, soon it evaporates and annihilated if it does not return to the safety of the Ocean.
Scientists believe that happiness is an inherent state of the mind. Once the mind is cleared of clutter and has clarity and focus, the mind returns to its inherent state of happiness. Mindful meditation removes thoughts that clutter the mind and allow the mind to be in its original state of happiness.
To Rumi, happiness is joining the source through the pathway of love that starts in the heart. Rumi believed a heart full of love and empty of ego is essential for connecting with the source that brings us happiness.