The ordinary man has the deep samskara ingrained in him that he is the body and that it is very, very insignificant, compared to the vast universe. Therefore the only possible mistake you are likely to be led into, while taking to the 'I'-thought, is the habitual samskara of the smallness attached to the 'I'.
This mistake is transcended by the contemplation of the aphorism 'Aham brahmasmi.' Brahman is the biggest imaginable conception of the human mind. The conception of bigness no doubt removes the idea of smallness. But the idea of bigness, which is also a limitation, remains over.
Ultimately, this idea of bigness has also to be removed by contemplating another aphorism: 'Prajnyanam asmi.' ('I am Consciousness.') Consciousness can never be considered to be either big or small. So you are automatically lifted beyond all opposites.