Many thinkers of the past commented that death was the primary problem in life - but this is apparently not the case for a typical modern person. How can this be?
The reason lies in the fundamental metaphysical assumptions of modern secular ideology: because the fundamental assumption is that the universe of everything is a mixture of rigid determination and randomness (don't ask me how!) and therefore death is merely to be expected: for moderns death is built-in and therefore 'not a problem'.
What IS a problem - a BIG problem - for moderns is understanding or explaining anything 'Good' - such as the values of truth, beauty and virtue; and also structuring principles such as purpose, meaning and relationships. What is a serious problem is why people (in a determined/ random, pointless universe) should be motivated to do anything, or even to exist.
How is this modern problem of 'nihilism', in practise, dealt with? First: it is not well dealt with - and modern societies are all demotivated and dying - both ideologically they are self-hating and biologically they are voluntarily going extinct by the basic failure to reproduce themselves.
But modern people nonetheless get up in the mornings, and do stuff, and mostly they try and stay healthy and alive - so the question is why?
The answer is - I think - related to the fact that moderns live in a perpetual adolescence - that is, a perpetual state between childhood and maturity; rejecting the spontaneous instinctiveness of childhood and rejecting the responsibilities and overview and long-termism of maturity.
What adolescents live-by is - in a word - fashion. Fashion is what defines the adolescent group, against children and against adults - fashion comes from peer groups - it has no intrinsic meaning but is random variation - yet it is mandatory, motivating, and taken with total seriousness. And then it changes, and changes again, forever and with no ultimate aim or reason.
Adolescents - and modern people generally - live in and for this perpetual bubble of the peer group. And this tells them what to do - but not why, except that otherwise they will lose peer status and that is the ultimate catastrophe because no greater or more lasting reality is acknowledged.
Modern people therefore live in a state of perpetual rebellion and unending transition - and this is what motivates. Such as it - feebly - is. Adolescents get angry, get into fights, have infatuations, will take great risks - and so do moderns.
But such motivations point nowhere, and over time, they go nowhere - because (from that perspective inside which they dwell) there is nowhere to go.
(Note: Christians recognise that, standing above all this random churning, are the forces of purposive evil; which ensure that the net direction of the whole system is toward destruction of The Good. But most of the modern people inside the bubble of perpetual adolescent rebellion are unaware of the fact, and would deny the possibility or reality of evil even if they were made aware.)