All those things and many more can be difficult but with each of them you know, "This, too, shall pass."
In my humble opinion the hardest thing about being a parent is having your kids grow up and move out on their own, because they'll never go back to being children.
But, if you're lucky, eventually they'll present you with grandkids.
If you're able to see them often you'll get to enjoy the cuddly babies, watch them learn to smile, walk, and talk, help them explore and enjoy the world as they grow, play with them, read to them, and enjoy all the other great things about children. Even grandparents who have custody of their grandkids have already been through the hard stuff with their own kids and that experience makes it all easier to handle.
As parents it's hard to imagine becoming a grandparent, but when and if that finally happens you'll be amazed at how much fun it is.