If a person is transcendental then what type of thoughts he should have to remain transcendental?

If a person is transcendental then he will very easily understand what’s spiritual life, Who Am I and Who is God and I’m spirit soul, part and parcel of that God so that’s why it is my eternal duty to serve him in love and devotion and that service in love and devotion is specified by Srila Rupa Goswami, Srila Prabhupada in their scriptures. According to your nature, propensity, mood, there are unlimited types of different relations with God, with Krishna. It is based upon different living entities. If somebody is transcendental, spiritually elevated then he will serve God, Krishna in that relationship and develop his love more more, more, higher level of consciousness which is called Krishna consciousness. The highest level of Krishna consciousness is that you will always be transcendental, for you heaven, hell or Golok Vrindavan becomes one and the same.
nārāyaṇa-parāḥ sarve
na kutaścana bibhyati
svargāpavarga-narakeṣv
api tulyārtha-darśinaḥ
If you will remain situated on transcendental platform and for you, heaven and hell, Golok Vrindavan becomes the same so your Guru will reveal you your nitya siddha swaroop, that nitya sewa, nitya service, eternal service that you would like to do, that will be revealed to you from within heart also, Krishna from within your heart will reveal to you.
ataḥ śrī-kṛṣṇa-nāmādi
na bhaved grāhyam indriyaiḥ
sevonmukhe hi jihvādau
svayam eva sphuraty adaḥ
Krishna svayam, Krishna will reveal himself to you from within your heart so this, this is what we should do on transcendental level. Transcendental service is very much desirable by You and Krishna because ultimately we want to reawaken our pure love for God and pure love can ‘only’ be, I would put word, ‘only’, pure love can ‘only’ be reawaken if you serve Him. Srila Prabhupada if you serve dog, dog will love you, and if you serve God, God will love you. So the best service, of course in this day and age is chanting holy name, 16 rounds but you can also serve Him in other respect which is natural for you, which is very easy for you to practice like cooking for Him, cleaning, distributing books for Him, writing books for Him, so many services to God.