Vanity of vanities, saith the Preacher, vanity of vanities; all is vanity.
In this world, and a mortal life; ultimately all is 'vanity': futility - evanescent and insubstantial as a mist, vapour, or breath upon cold air.
And from this there is no honest escape, and despair is the only honest reaction. To ask a Man to be satisfied with this life, to 'make the best' of this life, to 'count his blessings' and then to be content... is a counsel of despair – bleak, nihilistic, hope-less.
Unless there is more, unless there is something beyond this life, and something different and better in kind – then once we have raised the question of value we truly have no grounds for hope.
This is why secular self-help has the cumulative effect either of evasiveness and spin – or else induces a deepening despair.
The choice is stark: vanity or hope. Which of the two it is to be? This is a matter that should ultimately depend on what you most-deeply believe is true. (The advice of others will not suffice.)
If religion, strictly Christianity or something like it, is truly-false; then we must (because there is no alternative) live either without hope or with only a delusion of hope (and these amount to the same thing, in the end); subsist as best we may and by arbitrary, fleeting criteria.
If it is true, then (potentially) everything is changed, the world transformed; because hope is real.
Conviction cannot come from reason or evidence - at most it can be consistent with these. Conviction can only come from the heart, from deep within, from a primary understanding of the issue as a stark, existential dichotomy; and from a primary decision, a primary unforced-choice that is also an insight - knowledge of what is true, what is real.