One of the ways to tell how good your sanding job is to do the following.
After sanding rinse the section of with clean water look down the section done. If you like the way it looks great. If not keep sanding.
Water will imitate the way paint looks on your boat...it is all in the prep work. You can not make a paint job look good if the prep hasn't been done.
Check out page 4 of my link and you will see what I am talking about.
Don't give up now.
