Sri Chinmoy was asked, how one can tell whether one is meditating well, or just experiencing wishful thinking or mental hallucination. He answered:

“It is very easy to know. If you are meditating properly, you will get spontaneous inner joy. Nobody has given you good news, nobody has brought you any gifts, nobody has appreciated or admired you, nobody has done anything for you, but you will have an inner feeling of delight. If this happens, then you will know that you are meditating properly. But if you feel a mental tension or disturbance, then you will know that the kind of meditation that you are doing is not meant for you.”
– Sri Chinmoy

A good meditation is its own reward and fulfilment. During and after a good meditation, there is a natural clarity, simplicity, goodwill, optimism and ease. There is no disquiet, nagging doubts or grievance; the question of whether we are doing well or heading in the right direction, simply does not and cannot arise.

Sri Chinmoy continues:

“You will also know whether you had a good meditation by the way you feel afterwards. If peace, light, love and joy have come to the fore from within as a result of your meditation, then you will know that you have meditated well. If you have a good feeling for the world, if you see the world in a loving way in spite of its teeming imperfections, then you will know that your meditation was good. And if you have a dynamic feeling right after meditation, if you feel that you have come into the world to do something and become something – to grow into God’s very image and become His dedicated instrument – this indicates that you have had a good meditation.”
– Sri Chinmoy