Ornaments are exactly that! They ornament and grace the music. Although they are often the hardest thing to get right in a piece of music, they are also the least important part from a structural point of view.
This is why I usually leave them out when initially learning a piece, and I often recommend this to students. They are often technically and rhythmically difficult, and my experience has been that when they are not left out at the beginning of learning a piece, the student often does not learn the musical phrases and lines properly. The ornaments simply get in the way and confuse the often simple melody. If the students learns the melody first, they can shape it and phrase it, and get everything to sound correct. Then it is just a simple matter of fitting in each ornament into the correct place.
There is more to it that this though. The ornaments are not as important as the musical line. They are just there to grace the musical line. And when learned from the very beginning of the piece they often end up having too much prominence in the final performance. They are supposed to sound improvised and free; as if you just made them up on the spot! So next time you learn a piece full of ornament signs try ignoring them until you have the piece learned with the correct technique and expression. Then see how easy it is to add them in, and have them simply complement what is already a finished sounding piece of music.