1 Gita Sloka Every Day - Chapter 14 - Gunatraya Vibhaga Yoga - Sloka 18

The entire content of this mail is from Swami Adidevananda's translation of Ramanuja's  Gita  Bhashya and Swami Chidbhavananda's Bhagavad Gita, both published by Ramakrishna Mission

The ways of the three gunas are now explained

The Symptoms of the Gunas 11-18

1 Gita Sloka  Every Day - Chapter 14 - Gunatraya Vibhaga Yoga - Sloka 18

Urdhvam gacchanti sattva sthah madhye tishtanti rajasah I

Adhanya guna vritti sthah adhah gacchanti tamasah II sloka 18

ऊर्ध्वं गच्छन्ति सत्त्व स्थः मध्ये तिष्टन्ति राजसः I 

अधन्य गुण वृत्ति स्थः अधः गच्छन्ति तामसः II श्लोक 18

Those who are fixed in the sattva go upwards; the rajasikas remain in the  middle; and the tamasikas, abiding in the functions of the lowest gunas, go downwards.

There is an inviolable relationship between the change of the gunas in the jivatman and his being born high or low. The one fixed in sattva maybe born as a celestial if he is inclined towards enjoyment of pleasures. But if his bent is towards knowledge and wisdom he takes a suitable human birth and strives for further progress in that direction. The man of rajas is ever active in all of his births. For want of proper discrimination he does not head for higher births; nor does he detriorate intolower births. He maintains the position he has gained and waits for the dawn of discrimination to guide him upwards. But the man steeped in tamas wallows in the nether regions. 

Is it sufficicent if a man aspires to sattva and gets established there ? The answer comes in the next sloka.