In other words; one may overcome the angst and suffering generated by fear of the future, by means of training oneself in not-caring: not-caring whether one lives or dies - or even by seeking death.
This is the attitude advocated (whether directly or implicitly) by advocates of oneness spiritualties - Western derivatives of Eastern religions such as Hinduism and Buddhism.
(Oneness in the Western understanding is apparently not, in the same way, a feature of the actual religions in their native places; because there the religion is a whole way of social life - not individualistic; including elements such as the caste system in Hinduism, linked to a morally justified (karmic) system of reincarnation; and by related prohibitions on suicide.)
The proper task for Christians is therefore not to write-off this mortal life as a bad job, not to look-forward to the oblivion of death - but instead to be unafraid of death and welcoming when God decides, while also valuing this mortal life.
While the oneness solution to fear of death (and suffering) is indifference; the Christian solution should be through positive valuing: positively-valuing both the resurrected Heavenly life that comes after biological death; and also positively-valuing this mortal life which God has given us (and continues to give us) for our own eternal benefit, and the benefit of others.
Therefore, we ought to distinguish between those who overcome fear by indifference, and those who overcome fear by transcendent valuation.
The danger is that a world ruled by terror - and in which terror is encouraged; we may be over-impressed, and wrongly-impressed, by individuals who genuinely do not feel this terror - but who have achieved this by the wrong means - by devaluing life to the point that they have ceased to care about it.
This may be attained by a change of attitude induced by systems of meditative training; it may be achieved by other technologies, potentially including insights achieved using drugs such as Ayahuasca or other methods.
Such an attitude is not so much spiritual as therapeutic: it resembles a medical treatment of the emotion of fear - and as such we must be aware of the side-effects of this treatment when it works.
For a Christian; genuinely achieved indifference to life and death resembles the calm acceptance of nihilistic despair as a conviction of reality; which state is to reject salvation and desire hell.
However tempting the immediate relief from fear; an effective spirituality and world-explanation that is merely negative and therapeutic will do us, and also the world, more harm than good over the long-term.
We require instead a spirituality, rooted in a metaphysics, that is positive and motivating; and which sustains our valuing of this world, as-well-as the next.