See who is the doubter, who is the thinker. It is the ego. Hold it; the other thoughts will die away - the ego will be left pure. See the source from where the ego arises and abide in it. That is pure consciousness.
Ramana MaharshiEvery living being longs always to be happy, untainted by sorrow; and everyone has the greatest love for himself, which is solely due to the fact that happiness is his real nature. Hence, in order to realize that inherent and untainted happiness, which indeed he daily experiences when the mind is subdued in deep sleep, it is essential that he should know himself. For obtaining such knowledge the inquiry 'Who am I?' in quest of the Self is the best means.
Ramana Maharshi