Contemplating the Word “Echad (One)”
“ 'Shma Ysrael, Adonai Eloheynu Adonai Echad': Hear O Israel, the Lord our God, the Lord is One (Deuteronomy 6:6). When during this part of the prayer service a person recites the word ‘One,’ he should contemplate that the Holy One, blessed be He, is all that truly exists in the universe, for ‘the entire world is filled with His Glory’ (Isaiah 6:3). One must realize that he is nothing, for the essence of a person is his soul, and the soul is but a ‘portion of God Above’ (Shefa Tal 1a). Therefore, nothing truly exists except the Holy One, blessed be He.”
Rabbi Dov Ber of Mezeritch, Likkutim Yekarim (sec. 161)
The True “I”
“ ‘I, I am the One Who consoles you…’ (Isaiah 51:12). When one realizes that the true ‘I’ is God, and nothing else exists besides Him, then [the divine promise is fulfilled that] ‘I am the One Who consoles you.’ “
Rabbi Gedaliah of Linitz, Teshu’os Chen, Tzav (cited in Me’iras Einayim, Inyan “Emunah”)
Similarly, Ohr Ha-Ganuz La-Tzaddikim (Mattos) states:
“One must realize that essentially he, too, is Godliness. When one considers that the ‘self’ is really nothing, then Godliness will rest upon him.”
No Need to Go Any Farther
“It is not necessary to ‘place’ oneself in Godliness – but only to realize that everything is subsumed in the Divine Light.”
Rabbi Aharon Hakohen of Zhelikhov, Ohr Ha-Ganuz La-Tzaddikim (Vayera)
quoted by R' David Sears in "The Baal Shem Tov's Way of Meditation" at breslovcenter.blogspot.com
and from another essay by R' David Sears from the same blog "Living In The Present Moment", a teaching from R' Noson of Breslov:
Likkutei Halachot, Matanah 5
Every perceptive person understands that time does not exist. The past is gone, the future has not come, and the present is like the blink of an eye. Thus, the life of a man is only this instant in which he stands.
Consider this, and in whatever circumstance you may find yourself -- even in the depths of Hell --you will be able to cleave to G-d in each moment.
It is written: "See, now, that I, I am He..." (Deuteronomy 32:39):
See now, precisely. Through the paradigm of now, you are able to see that I, I am He and begin anew, in each moment, to cleave to G-d.