No person can know his own inner motives.
He may be kind because kindness brings him pleasure.
He may be wise because wisdom is music to his soul.
He may become a martyr burned in fire because his heart burns with defiance.
How can you know that your motives are sincere? What is the test?
The test will be when doing the right thing cuts against the grain.
Torah Ohr 19b; Likkutei Sichot, vol. 20, pp. 76, 306–307.