I have had the vision of exactly what I want in a garment floating around in my head for several months now. I tried several times to modify existing patterns to my idea and always the finished product wasn't quite right.
The bodice was too big...It didn't come together the way I wanted it to in the center...it was too tight under the arms... You get the picture.
At least five "almosts" later I was successful in creating The Frankentank. It had everything I wanted. Correctly fitting straps, a snug bodice, and a skirt that had a nice drape to cover the squishier parts of my..ahem...waistline.
The message here? Don't give up on YOUR vision.
Consult stitch dictionaries and patterns. Look closely at garments that are similar to get a feel for how an element was done. Ask other fiber artists what they would do in cases where you're coming up against roadblocks. Make similar items to get a better understanding of the flow and keep asking yourself questions.
Would I have more control over the drape going bottom up or top down? Is the yarn right? Would a taller or shorter stitch work better?
With each try you will learn one or two new things and you will be able to create what your minds eye sees. Remember, with crochet almost all things are possible.