Hey, welcome to the community! Always great to see someone discovering the genre.
I totally get what you mean about the sad side of post-rock. There's a lot of it, and some of it hits hard. But there's plenty of hopeful, uplifting stuff too.
If you haven't checked them out yet, Explosions in the Sky is probably the first band that comes to mind for hopeful post-rock. Their album "The Earth Is Not a Cold Dead Place" is basically the definition of what you're looking for. "Your Hand in Mine" and "First Breath After Coma" are both about new beginnings and moving forward.
Another favorite of mine is And So I Watch You From Afar (ASIWYFA). Their self-titled album is pure joyful energy guitars bouncing off each other, nothing bleak about it. Try "Set Guitars to Kill" if you want something that actually makes you feel like jumping around.
God Is an Astronaut is also worth your time. They lean more uplifting and driving. "All Is Violent, All Is Bright" has some incredible moments that feel more expansive and hopeful than sad.
And if you want something more on the thoughtful/contemplative side that isn't sad, The Album Leaf is great. Gentle, warm, optimistic "Into the Blue Again" is a good starting point.
What kind of music were you listening to before you found post-rock? Always curious what draws people in.