According to the teachings of the Buddha, one reason people may be unhappy is that they are not living in the present moment.
The Buddha taught that the mind is often caught up in thoughts about the past or the future and that this mental wandering can cause suffering.
When we are lost in regrets about the past or worries about the future, we are not fully present in the here and now, and we miss out on the joy and beauty that is available to us in the present moment.
By cultivating mindfulness and staying present in the here and now, we can find greater peace and happiness.