You are what you think...

Man's whole conduct in life depends upon what he holds in his thought.

Bowl of Saki, by Hazrat Inayat Khan

Commentary by Pir-o-Murshid Inayat Khan:

The heart, which is called a mirror in Sufi terms, has two different actions
which it performs. Whatever is reflected in the heart does not only remain a
reflection but becomes a creative power, productive of a phenomenon of a similar
nature. For instance a heart which is holding in itself and reflecting the rose,
will find roses everywhere. Roses will be attracted to that heart; roses will be
produced from it and for it. As this reflection becomes stronger, so it becomes
creative of the phenomenon of roses. The heart that holds and reflects a wound
will find wounds everywhere, will attract wounds, will create wounds; for that
is the nature of the phenomenon of reflection. ... There is another aspect of
this reflection, and that is what one thinks, one becomes. One becomes
identified with it. Therefore, the object which is in one's thought becomes
one's own property, one's own quality.

A person (lacking mastery) holds a thought in mind, whether it is beneficial to
him or not, without knowing the result which will come from it. It is like a
child who holds a rattle in his hand and hits his head with the rattle and cries
with the pain, and yet does not throw the rattle away. There are many who keep
in their mind a thought of illness or a thought of unkindness done to them by
someone and suffer from it, yet not knowing what it is that makes them suffer
so, nor understanding the reason of their suffering.

Man's whole conduct in life depends upon what he holds in his thought. The
thought of the wicked produces in him wickedness, and the thought of the good
creates goodness. The love of Rasul, the divine ideal, enables one to
concentrate upon this ideal. Since all in the garb of matter are to be separated
one day in life, good or wicked, friends or foes, what alone is reliable is the
ideal which man creates within himself, call it Christ, Buddha, Krishna or
Muhammad.