Is it obligatory to recall the meaning of the Prophetic invocations (adhkar) and litanies (awrad) with the heart while uttering them with the tongue, if the heart is preoccupied with other matters?

"What is prescribed is the heart's concordance with the tongue to benefit from remembrance (dhikr). Therefore, you must strive to ponder what you say, and if the heart is occasionally heedless, there is no harm. We advise you to frequently seek refuge with Allah from Satan when experiencing (evil) whisperings."