The key to the meaning of Life is purpose - to know what Life is For.
Most discussions of the meaning of life (including most Christian discussions) ignore as unimportant the truly vast diversity of actual human lives. Yet these are extremely variable - even from a purely biological and socio-political 'materialist' perspective.
Some people die immediately after the fertilised egg is formed; others die in the womb as embryos or as a more developed foetus; some die at the time of birth, or as infants; others die in childhood or as adolescents. Taken together - these 'premature' deaths account for a large majority of humans throughout history.
Then among the adults, there is a wide range of life expectancy. Then there is the variety of societies - hunter-gatherers, farmers or post-industrial revolution. There are widely different climates - between the Arctic and the Deserts, with all kinds of temperate and tropical environments in between.
There have been huge differences in human life through history, illiterate and literate, small scale and very large organisation. There are differences between political systems and regimes. And even when all such distinctions have been noticed, there are massive differences between classes, races, degrees of health and types of disability and illness.
Finally there is the specific family situation - parent/s or some other form of care, sibling/s or not, extended family or not, neighbours...
So, there are two aspects to life - the generic and the specific; the aspects that we all share and those which are partially or wholly distinctive to our own situation. Any satisfactory description of the meaning of life either needs to encompass both - or else to explain why one universal meaning of Life comes to be associated with such a vast range of individual variety.
My understanding is therefore that there are (at least) two different meanings of life:
1. Life. A single and universal meaning of 'human life' that applies to everyone who ever lived or will live.
2. My Life. An unique meaning of specific lives, that applies only to each individual person and their unique nature and circumstances.
My further understanding is that the meaning of Life is related to incarnation - to 'getting a body'. In brief - we all live this mortal life because we need to have a mortal (temporary) body, in order that after this life we are able to choose to accept the gift of resurrected eternal life, that Jesus brought.
In other words, we need a mortal body in order to be able to have a resurrected and eternal body. This meaning is universal: there is one meaning for all.
In sum the purpose of Life is incarnation, and the meaning of Life is to make possible resurrection into Heaven (for those who choose it, who choose to follow Jesus - i.e. those who choose the path of salvation).
The meaning of My Life - by contrast - is unique; just as my life situation is unique. I need to add a further assumption at this point: that each incarnated soul is already unique. Therefore, the uniqueness of our nature and life situation is a consequence of our uniqueness as newly incarnated souls.
So, I am assuming that we existed pre-mortally, as a wide range of unique not-incarnated spirits. This uniqueness is partly from distinctive experiences in pre-mortal life; but is ultimately founded on our origins as unique primordial Beings, potential-Men, present before creation and before we were made children of God.
In sum, the uniqueness of our mortal natures and lives derives from our original uniqueness. To put it another way; humans were never the same, at any point. We began as different from each other, we remain different from each other and our future is one in which each resurrected Man is unique.
The Self is therefore primary, and A Good Thing. God's plan for creation entails that we each are and remain unique. One consequence is that - overall - the experiences of this mortal life are intended to make us more distinctively unique.
If there was nothing else to it; the encouragement of human distinctiveness would tend to lead to disintegration of creation - everybody pursuing his or her own unique goals... But the primary reality of Christians is Love; and it is Love that enables unique individuals to live in harmony, to create in harmony.
My particular nature and circumstances in My Life are related to the particular needs of my soul. Each life offers experience; and my assumption is that (since this is a God-created world, and we are each a beloved child of God) the actual experience of My Life is intended for that learning from which I would most benefit.
This specific mortal life is therefore for learning - at one extreme some need to learn a lot (i.e. would benefit from significant learning) and may have long and complex lives. At the other extreme, other individuals do not need to learn anything specific beyond the bare facts of physical incarnation, and perhaps certain simple realities to do with being alive, dependence, basic sensation... and these would include some of those who die in very early, perhaps as zygotes, embryos or a foetus - even without the womb.
In sum, the purpose of My Life is to provide the experiences necessary for me to learn what I most need to learn in taking up my post-mortal life in Heaven.
This further means that My Life, this actual mortal life, does not have any meaning for those who reject salvation.
In other words, when mainstream atheistic, God, rejecting, Christ rejecting, people often express a belief that 'life has no meaning' - they are correct. From their point of view, their specific lives do not have any specific meaning.
The specific details of actual human lives are only necessary for that specific person, and only in relation to the destination of resurrected eternal life. If that is not going to happen; then life truly is pointless.
Bluntly: if you don't want resurrection, if you don't want to dwell in Heaven, if you don't want to follow Jesus... then actual mortal life is indeed a waste of your time, as you probably suspect already.