You won't know either way. Few people die knowing they will.
You’re dead though. What does it matter?
But then again, nothing makes you feel more empty than achieving a goal...
That's not my experience. I need to be making progress to be sane. Achieving something small everyday makes me have confidence in life and a sense of control. This is crucial to keep existential dread at bay. I have a calendar where I track life events (good and bad). It's wonderful to look back and remember that, tlin the last two years, even though I feel like I haven't changed, actually a lot has.
Achieving something is hence a source of joy. But so is eating food.
Achieving something evokes a feeling of loss that you have to bear until you've found whatever is next. It's not unlike experiencing a death or break-up. This happens when you finish a book, video game, or TV show you've invested a fair bit of time in. We are driven to cope with this feeling by seeking what's next.