The problem with achieving happiness is the way the human mind is designed by evolution to process the world from an egocentric perspective and focus on the threats that might shorten our lives. Socially dependent on others, egocentric children grow into adults who may be less self-centred but end up becoming dissatisfied because we are prone to focus on the wrong information and comparisons when it comes to evaluating our lives.
We need to get out of our heads by connecting with others and the world around us through practices that have proven to make us happier.