@Persona phil,
Whether it makes sense to say there is something we can call "human nature" in any kind of definitive way, or to then single out one particular trait within "human nature" is a very moot question, given the complexity and ambiguity of human existences as lived by the Self.
And if we propose a list of examples of this struggle, we find a plethora of different kinds of struggle that, it seems, makes the use of one word to describe what is going on extremely tenuous.
We see, or want to see, the struggle of Beethoven to compose a symphony on his messy scores. We see, or want to see, the struggle of a young boy to master a tricky shot on the pool table.
We see in many the struggle to overcome physical problems or to overcome addiction. We see in others the struggle to avoid what they see as sinful thinking or behaviour. We see in combat, one soldier struggling to keep himself and his comrades alive in a firefight.We see an actor struggling to memorise the lines of his character. We see other beacons of light risking their lives in a struggle against untruth and intellectual oppression.
From a personal to a social level, the same multiplicity can be illustrated from 5000 years of recorded history. The struggle of a people to maintain their identity and territory against more powerful neighbors, the struggle of workers to unionise, the struggle of a orchestra to achieve a perfect performance, the struggle of authors to find a way to publish in a closed society, the struggle between four claimants and their adherents for the Empire of Rome. And so on.
Hobbes saw human nature as a perpetual war of all against all, others saw it to be just the opposite and pointed to the noble savage; so not only is human existence extremely complicated, but no one can agree on which accurately describes human nature.