Content is there in text editor but only part of it is there in visual editor

[ Moderator note: moved to Fixing WordPress. ]

I wrote a big post and was wondering why it wasn’t converting well when it was seeing a good amount of traffic. I clicked on it to check my links and lone behold most of the content is missing. So I went in to check it out and all the text is there in the text editor but most of the post is missing when I click over to the visual side of things. Can anyone tell me what went wrong and how I can fix it? I usually write my posts on the visual side and only pop over to the text editor to add in code for an affiliate banner if I need too.