Faintheartedness and fear sometimes come in the guise of sattva but are actually tamsaic in origin. In one of his commentaries on the Gita, Swami Vivekananda says (Complete Works, V4, p 107-10; available here - Vol 4, 'Lectures and Discourses', 'Thoughts on the Gita' https://advaitaashrama.org/cw/content.php):
The next is, Nishkâma Karma, or work without desire or attachment. People nowadays understand what is meant by this in various ways. Some say what is implied by being unattached is to become purposeless. If that were its real meaning, then heartless brutes and the walls would be the best exponents of the performance of Nishkama Karma. Many others, again, give the example of Janaka, and wish themselves to be equally recognised as past masters in the practice of Nishkama Karma! Janaka (lit. father) did not acquire that distinction by bringing forth children, but these people all want to be Janakas, with the sole qualification of being the fathers of a brood of children! No! The true Nishkama Karmi (performer of work without desire) is neither to be like a brute, nor to be inert, nor heartless. He is not Tâmasika but of pure Sattva. His heart is so full of love and sympathy that he can embrace the whole world with his love. The world at large cannot generally comprehend his all-embracing love and sympathy.
The reconciliation of the different paths of Dharma, and work without desire or attachment — these are the two special characteristics of the Gita.
Let us now read a little from the second chapter.
To him who was thus overwhelmed with pity and sorrowing, and whose eyes were dimmed with tears, Madhusudana spoke these words.
The Blessed Lord said:
In such a strait, whence comes upon thee, O Arjuna, this dejection, un-Aryan-like, disgraceful, and contrary to the attainment of heaven?
Yield not to unmanliness, O son of Prithâ! Ill doth it become thee. Cast off this mean faint-heartedness and arise, O scorcher of shine enemies!"
In the Shlokas beginning with , how poetically, how beautifully, has Arjuna's real position been painted! Then Shri Krishna advises Arjuna; and in the words etc., why is he goading Arjuna to fight? Because it was not that the disinclination of Arjuna to fight arose out of the overwhelming predominance of pure Sattva Guna; it was all Tamas that brought on this unwillingness. The nature of a man of Sattva Guna is, that he is equally calm in all situations in life — whether it be prosperity or adversity. But Arjuna was afraid, he was overwhelmed with pity. That he had the instinct and the inclination to fight is proved by the simple fact that he came to the battle-field with no other purpose than that. Frequently in our lives also such things are seen to happen. Many people think they are Sâttvika by nature, but they are really nothing but Tâmasika. Many living in an uncleanly way regard themselves as Paramahamsas! Why? Because the Shâstras say that Paramahamsas live like one inert, or mad, or like an unclean spirit. Paramahamsas are compared to children, but here it should be understood that the comparison is one-sided. The Paramahamsa and the child are not one and non-different. They only appear similar, being the two extreme poles, as it were. One has reached to a state beyond Jnana, and the other has not got even an inkling of Jnana. The quickest and the gentlest vibrations of light are both beyond the reach of our ordinary vision; but in the one it is intense heat, and in the other it may be said to be almost without any heat. So it is with the opposite qualities of Sattva and Tamas. They seem in some respects to be the same, no doubt, but there is a world of difference between them. The Tamoguna loves very much to array itself in the garb of the Sattva. Here, in Arjuna, the mighty warrior, it has come under the guise of Dayâ (pity).
In order to remove this delusion which had overtaken Arjuna, what did the Bhagavân say? As I always preach that you should not decry a man by calling him a sinner, but that you should draw his attention to the omnipotent power that is in him, in the same way does the Bhagavan speak to Arjuna. — "It doth not befit thee!" "Thou art Atman imperishable, beyond all evil. Having forgotten thy real nature, thou hast, by thinking thyself a sinner, as one afflicted with bodily evils and mental grief, thou hast made thyself so — this doth not befit thee!" — so says the Bhagavan: — Yield not to unmanliness, O son of Pritha. There is in the world neither sin nor misery, neither disease nor grief; if there is anything in the world which can be called sin, it is this — 'fear'; know that any work which brings out the latent power in thee is Punya (virtue); and that which makes thy body and mind weak is, verily, sin. Shake off this weakness, this faintheartedness! — Thou art a hero, a Vira; this is unbecoming of thee."
If you, my sons, can proclaim this message to the world — — then all this disease, grief, sin, and sorrow will vanish from off the face of the earth in three days. All these ideas of weakness will be nowhere. Now it is everywhere — this current of the vibration of fear. Reverse the current: bring in the opposite vibration, and behold the magic transformation! Thou art omnipotent — go, go to the mouth of the cannon, fear not.
Hate not the most abject sinner, fool; not to his exterior. Turn thy gaze inward, where resides the Paramâtman. Proclaim to the whole world with trumpet voice, "There is no sin in thee, there is no misery in thee; thou art the reservoir of omnipotent power. Arise, awake, and manifest the Divinity within!"
If one reads this one Shloka —
— one gets all the merits of reading the entire Gita; for in this one Shloka lies imbedded the whole Message of the Gita.