Here's a handy, dandy little trick I learned from Creating Keepsakes magazine:
If you love to edit your pics w/ Instagram, but don't *always* want to share them, here's what you do:
Before you go into Instagram, put your phone (or tablet) on Airplane Mode. Open Instagram & edit your photo as usual. When you're done, click Share. It will take you back to your feed & tell you that your feed can't be refreshed. But, when you go to your camera roll, there's your picture, saved, but not shared w/ your followers! (Don't forget to take your device off of Airplane Mode when finished.)
Yay! I love this option!! Hope this helps & you find it useful too!! :)