Buddha Purnima reminds us of three crucial turns of life: Birth, realisation and death. In other words, it comes as a reminder to mind the purpose of life.
Buddha and the religion that goes by his name (Buddha never evolved his own religion) tell us to realise that one is born because one is incomplete. Therefore, the new life one gets is a precious gift that can be moulded in any manner one wishes to. He gets a chance to reform himself and be in constant search for an end to that endless journey.
The moment one is born, one gets subjected to 'samsara', which is due to avidhya (unawareness). That leads one into various unhealthy situations, which in turn takes one away from the path of realisation.
The Buddha says one has to strive hard to attain the knowledge to have a clear perception. Only then one can acquire samata (unshakeable calm). This can then lead to direct intellectual intuition of the reality.
The Buddha's concept of reality comes out clear in the following words:" I deem the highest goal of a man to be the stage in which there is no old age nor fear, nor disease, nor death, nor anxieties, and in which there is no continuous renewal of activity."
Dr.R. Radhakrishnan says that the state of mind that one attains after realisation of the Truth is not a state of life being in paradise where gods dwell. The reason being that gods belong to the world of manifestation and, therefore, one can't call it absolutely unconditioned. The ultimate goal is beyond existence and non-existence. The state of the mukta (the Buddha) is higher than that of the Brahma. It is invisible, resplended and eternal.
And, what is more important, it is within everybody's reach. Only that one has to strive hard by following the path of dharma with complete consciousness of the purpose of life. And to realise that the Buddha too was just like you and me. But our perception towards the purpose of life has set us apart.