Our understanding of the basic set-up of life, the human condition, God's plan of salvation; needs to take into account the nature of things as we experience them.
Although Men are seeded with divinity, and have inklings of the highest aspirations, and are capable of love; we find ourselves to be unstable, foolish and prone to lapse into wickedness when confronted with a world of temptations and problems.
Christ, by contrast, did not sin - He was tempted and suffered - but He was strong and wholly good. We, however, are not like that.
From this I infer that the yielding to temptation is not necessary to our spiritual growth - it is better to resist temptation (like Christ).
BUT - the basic situation is that we cannot in fact resist temptations. Although we are not intended to fail in any specific situation, the fact is that as weak creatures in a world of temptations and problems, we will fail - again and again and again.
We are therefore meant to learn by trial and error.
So the primary weapon for humans against the world is not resisting temptation, is not 'being good' - the primary weapon is repentance.
We will fail, again and again, and therefore the important thing is what we do when we have failed.
Repentance is a tricky concept - but one way to think of it is that Christ made it possible for all humans to repent under any and all circumstances.
Repentance is (now, because of Christ) always possible to anyone; and always effective.
In a sense, we are here in order to repent; repentance is in one vital thing we must do, and can always do.
By this account, pride is simply the refusal to repent - therefore pride is the worst possible sin.
All the ultimate wickedness in the world can (crudely) be reduced to this - pride preventing repentance.
This may seem negative - but the other side of the coin is that life is an adventure with real stakes; but a safe adventure.
We must do our best, but we will fail again and again to achieve what we aspire to and to avoid what we want to avoid.
However we are ultimately safe and our immortal souls and eternal happiness cannot be harmed by anything the world can throw at us - so long as we repent in a final and ultimate sense.
Minimally, that is what life is for: to try, fail, repent.
(The topic of 'what exactly is repentance?' will require separate consideration. Here I want to establish that repentance- whether explicit or more usually implicit - is the single most important thing in this mortal incarnate life; without which it would - literally - have been better not to have lived at all.)