You're right. Of course you're right; you've been working on it a long time and you are intimately acquainted with all the details. There is no way anybody could have your insights on this client/product/market.
And yet, there is The Power of Two: share your thinking with another and test its robustness. Stay open-minded and be willing to listen, to shift, to improve. No, not compromise. Come up with an even better solution or idea.
It's very powerful when linked with The Power of One.