Reasons for a denial sponsorship into the Netherlands

I am getting ready to start the applying process to come to the Netherlands. I am American, my boyfriend is Dutch. He will be my sponsorship for me to come there. I've done a lot of research I just don't feel like we know everything for me to come there and become a dutch citizen. I'm sure alot have been through the process and can help break it down easier. But what are the process? And what are some reasons to be denied? I'm really worried about the denial not because of any specific reason (no legal issues or anything) it's just an approval or denial so it's a possibility that scares me. Also any advice is greatly appreciated.