Yeah, it's normal.
What you're describing is part of the process. It's called suicidal ambivalence. People can feel both certain and unsure at the same time. It doesn't mean your decision is impulsive or invalid. It means your survival instinct is still doing its job, right up until the end.
Survival instinct is physiological. It's your body doing what it's wired to do which is keeping you alive at all costs. It doesn't care about your quality of life or long term suffering. It can show up as physical symptoms: racing heart, shallow breathing, nausea, dizziness, or sudden panic even when your mind is calm.
Cold feet, on the other hand, usually comes from psychological uncertainty. It sounds like: "What if this gets better?" or "What if I regret this?" or "I'm not sure I've really tried everything." It's cognitive. If you're sitting there evaluating your reasons, rethinking the plan, wondering what might happen to people around you, that deserves time and reflection.
Most people feel this. Take your time. Breathe through it. No shame in feeling both ready and afraid. No shame in rethinking and putting plans on pause.