How do I carry the weight of being the last check before something ships?

You can validate to certainty, and that is exactly why the weight sits on you. You are the final gate before something people depend on goes live. Everyone leans on your yes. That is a heavy thing to carry, and feeling its full weight means you understand what is at stake. Carry it, but carry it rightly. Your job is to do the check thoroughly and honestly, with the rigor you are known for. What you cannot do is become the sole owner of every possible outcome, because a safe system is built by many hands, designers, makers, reviewers, not resting on one person's shoulders at the end. When you take on the whole burden alone, you are carrying weight that was never meant to be yours alone. Do two things for yourself. Trust your process, so that when you have done the check properly, you can rest in having done it well rather than in guaranteeing the universe. And push, gently and repeatedly, for quality to be built in earlier, so you are the last line and not the only one. You are meant to be a strong check, not an atlas holding up the sky.