It makes or breaks you, my friend.
Have you ever picked up a book, loved the cover, loved the back cover and opened it to the first chapter only to put it back after the first paragraph?
Why did you put it down?
I bet I know why. It didn’t grab you by the junk and scream “Read me!”
If your first paragraph is weak, readers will assume all your work is. Bring your A-game, boys and girls, and make that first chapter sing.
Ask yourself, am I starting too early?
How is that all-important first line?
Do you have a good, solid critique partner/group that will rip it to shreds and offer mind blowing advice?
There are many elements that help engross a reader, and not everything works for every person. The better that opening is, the more people you will appeal to. After all, you catch more flies with honey than vinegar, so set your trap wisely, my friend.
Wisdumb is easy to come by. 
It has been my experience that the first chapter and the last chapter are the hardest. You want to grab people and provoke them into reading your book with the first. (I must have written my first chapter a million times before I finally found the right place and the right time to start my characters stories–I can only pray I’m finally right, haha)
But that last chapter… it also has to be amongst the best writing in the novel… for if it falls short, good luck getting people to pick up the next novel you write. I’m sure I’ll end up with a million endings, just like I ended up with a million beginnings before I’m satisfied. The difference is, it’s easier to tell where a story ends than it is to figure out where it begins. At least, that’s been the finding I’ve had with the current WIP.
Excellent point, Justine!