I was always struck by CS Lewis's hardline attitude to happiness or self-gratification in relation to Christianity - the way he emphasized the problem of mixing-up the 'therapeutic' aspect of belief with the business of what is actually true.
In the Screwtape Letters and Great Divorce (as well as his more abstractly theological works) Lewis negatively depicted people who fluently excused whatever they wanted to do - what they currently enjoyed doing, or what made them feel better - by making arguments that linked these to Christianity.
In the Narnia chronicles; this was encapsulated in the phrase stating that Aslan (i.e. Jesus) is Not a Tame Lion. That is to say; Christianity cannot be comfortably domesticated and stay Christian.
Certainly it is a real problem; but - especially in The Last Battle - Lewis also depicted the opposite problem, which happens when the cruelty and destructiveness of the evil demon Tash is explained as being the actions of Aslan; or later, the oxymoronic false-invention Tashlan, syncretized from both good and evil deities.
These actual evils - in reality motivated by greed, selfishness and sadism - were effectively propagandized as consistent with the fact that Aslan is Not a Tame Lion
And therefore the fact that God is not aiming at our immediate self-gratification is twisted into a mask for 'the devil'.
In other words; on the one hand it is true that, at a superficial level of here-and-now, the goodness of God may be experienced as harsh life-lessons that are, nonetheless, necessary for our ultimate and eternal benefit.
Yet, on the other hand, to know when this is actually the case, and when evil outcomes are instead a product of evil intent; requires honest discernment as to the motivations.
So, the experienced and observed miseries and sufferings of this world are not evidence in either direction - they might be necessary and temporary means to a good end; or they might be the end in itself: cruelty, destruction, misery, suffering might be the actual purpose of evil beings.
The correct answer must come from discernment, and the discernment - while taking-account-of-evidence, cannot derive-from evidence.
As always, we are driven down to an acknowledgment that all knowledge depends on intuition; an individual act of an individual being.
And, further, that Christian discernment entails acknowledgement that there is a side of Good (i.e. God) and a side of evil (i.e. the demons). We first need to know this in order to choose one or the other side; and only by choosing a side can be - even in principle - make a discernment as to whether a particular event was motivated by good or evil intent.
For a Christian; to deny that good and evil are separate and opposite sides, amounts to the false-deity of Tashlan - in other words, to base discernment on an assumption of unity, oneness, 'non-dualism' is itself (merely) a type of evil.
From this analysis we can see that Christianity is related to self-gratification (i.e. the pleasurable, comfortable, desirable) in that God wants us to be deeply and eternally happy; but such a goal entails that we must sometimes be temporarily and superficially miserable.
To know what is going-on in the here and now we need to depend on divine guidance - which (because God is The Creator, is Good, and is our loving parent/s) we have all been equipped-with.
We all have potentially available both direct access (i.e. in our stream of thinking) to true inner guidance (because we have within-us something of the divine, being children of God)...
And this inner guidance also enables us to have access indirectly to external guidance - both directly from the Holy Ghost, and indirectly from all other sources of information such as legitimate and wise authority (e.g. of Men and books), true-tradition, and any other cultural product.
In sum; deep self-gratification is a sure guide to the operations of God and His agents; while superficial self-gratification may be a consequence of the manipulations - or sadism - of evil Men and/or the beings of supernatural evil.