In evaluating this world we live-in as mortal incarnate Men, the standard by which we should judge it is not in terms of whether it is as happy and as pain-free as it possibly could be. Clearly it is not optimal in terms of pleasure and comfort; but that is not the function or purpose of this world.
The function of this world is to be the best possible kind of place for building gods: that is, to be the best kind of place for theosis, sanctification, spiritual progression.
That is our destiny - in the sense of our chosen and appointed task.
Our general destiny (purpose in life) is common to Mankind, but also unique - because each soul is unique, and significantly and importantly distinct.
We are each born into a specific time, place and circumstances - was this merely random?
Clearly not - that would be to sabotage destiny.
Therefore, since our situation was not random then it must be (to some extent) intended, planned in some way; but how intended?
Not one way but several.
Each of our specific, personal destinies was:
1. Chosen by us (as pre-mortal un-incarnated spiritual beings) - on the basis of what we want.
2. Allocated by God - on the basis of what is good for us (as individuals).
3. Modified and constrained by our choices and the choices of people around us (and the workings of the 'laws' of space, time, mass etc.) - thus modified and constrained by freedom and contingency.
Presumably, what happened - the specific time, place and situation - took into account these various considerations.
And this is the basic human condition.
We were placed in a time, place and circumstance - that was not random chance; but the placing had to take into account distinct considerations, was only in general and in a compromised sense, and the situation of placement is necessarily open to change.
Our personal destiny is specific but constrained and (in a sense) approximate; and also subject to modification and evolution.