But if our assumptions are that this mortal life is for our learning - so that we can have useful experiences and learn stuff that is necessary (or at-least very beneficial) - for salvation and resurrection to eternal life...
And if we also assume that God is the creator who sustains our life, and that God loves us each individually as divine children...
Then the usual baseline assumption must be that we remain alive because we have some-thing important we can and should be learning from our life.
Therefore, to plan a suicide will typically entail a refusal to learn from our mortal lives, which is a rejection of God's plans for us; and the more planned, the more pre-meditated, the suicide - the more likely this is to be the case.
And when suicide is 'assisted', then actual evil has become involved in the motivation; because assisted suicide is done by a bureaucratic System; and bureaucracy is essentially evil in its nature and effects: plus our actually-existing System-bureaucracy in The West is anti-spiritual, anti-Christian, and pro-Satanic.
So - of its nature - assisted suicide amounts to an act that is both (almost always) evil in motivation, and also an invitation of evil into the heart.
National suicide is the failure of a culture, a society, to reproduce itself - both materially and spiritually; but most obviously the national suicide of chosen sub-fertility... That is, a societal decision not to have children even at the minimum replacement level - and 'chosen' strategically; despite the availability of sufficient (indeed excessive) national resources; and despite national prosperity, comfort, peace etc. - which ought to support greater levels of child-rearing.
Sub-fertility (now universal in all developed nations, and increasingly gross - especially among native populations) is diagnostic of a profound spiritual malaise that amounts to a covert desire for cultural self-annihilation - i.e. suicide.
Such strategic suicide is an act of defiance against God; and a deliberate refusal to learn whatever God has created and maintained the nation for.
National - like personal - suicide by deliberate sub-fertility is an invitation of evil into the heart; as is apparent from the demonic ruling class who now administer and control all the Western nations. These evil Beings (mostly human, some demonic) are invited, tolerated, enabled, trusted, cooperated-with, and actively approved by the intellectual-class servants...
And these national leaders are easily able to persuade an already self-corrupted populace to accept their inverted value system and become further corrupted. The populace now widely espouse a morality that despises the national culture, loathes patriotism, and which values and privileges any alien over natives.
Our current subsidized, organized, and sustained mass immigration - and the values that justify and sustain it - is therefore an instance of assisted suicide at the national level.
In sum: when suicide is a sin (a deliberate turning away from God's creative intentions), then this is because of its motivation; but assisted suicide is always a sin, because the motivation is strategic hence responsible, and is compounded by its being an invitation to evil.