In 'life', it's of the utmost importance, I'd have to argue. But that's obvious.
If by
life you mean the essential, most basic, and seemingly only evolutionary "purpose" of an organism's existence, then yes, and that's obvious.
A notable exception would be organisms that do not require sexual reproduction for the proliferation of its species (via evolved processes such as parthenogenesis, bacterial conjugation, vegetative propagation, agamogenesis, fragmentation, sporogenesis, nucellar embryony, etc.)
But I'd surmise any person even vaguely familiar with biology 101 knows that reproduction—in whatever form; sexually or not—is vitally
necessary for a species' survival and continuation. However, necessity and importance are not synonymous. To argue that sex (for homo sapiens, say) is a necessity is an incontrovertible argument that's corroborated by biology and other sciences, their data, and, though I hate the term, common sense.
But importance is a matter of priority, not necessity. If the continuation of a species is not its priority, then its continuation is of necessity but of no importance.
Importance is subjective and necessity is not. If you think X is unimportant for Y, than it is. But thinking X is unnecessary for Y has no bearing on X's necessity for Y.
Therefore, sex is only of "utmost importance" if you believe it is of "utmost importance" to reproduce and continue our species.
I tend to think everything is geared with 'sex' in heart. Or I guess I'd challenge that.
You don't have to challenge it, as I'm willing and presumably better able to challenge it for you.
If everything means every living thing or every organism, this erroneous notion or “thought“ is only true insofar as one ignores the thousands of species of life that do not sexually reproduce (and therefore cannot possibly have "sex in their hearts"; some don't even have hearts), pretend the >5% of asexual (or nonsexual or sexually-disinterested) people and other animals in the overall population don't exist, and overlook the willfully celibate or chaste individuals who abstain from sex or thoughts of sex for the duration of their lives for spiritual reasons (like monks, say).
So then, with well over half of the animal kingdom excluded, your idea goes from completely wrong to mostly wrong.
And I hadn't a clue sex was in one's heart, anyway. I always thought that if sex had a provenance, it would be the pudenda or my penis. At least that's where the tingling and tumescence I experience upon the sight of a titillating zaftig girl comes from. Though there's an accompanying mild tachycardia, the phallus seems most salient both in terms of symptomology and physicality (i.e., the imposing and impressive protuberance that even Priapus would envy. Ha! ).
