I've been looking at this off and on the last day or two. It's a very pretty picture and looks to me to be decently exposed (tiny bit blown out) and takes advantage of the light and sky.
However, the straight line of the path goes up the middle of the lower portion of the shot and to me seems to make it a bit boring. The tire track(s) detract even more from the path.
Straight lines are hard to deal with in nature shots and paths 18" wide and wider are usually not natural. A curve, like what looks like is further up the trail may give the shot a more comfortable feel and possibly provide the raking light to add to the composition.
You've made good use of the clouds and shape of the cactus together. I can see why it caught your eye. As I mentioned, the bottom falls apart a bit.
When you see something like this I suggest looking for an item of interest for the foreground. Look for leading lines and curves (objects and light) taking you to the subject. Not like drafting or mechanically, but like art.
It's all subjective. Everybody looks for different things. I think it has a lot to do with feeling also. Express what you feel; express why you feel this is the most beautiful cactus at this moment, and why you have brought the viewer here to show them this incredible scene. Work to make every shot the best work you have ever done. Sounds like it sucks, but once you get into the mode it's very enjoyable.
Here's another question for you to answer;
http://www.thephotoforum.com/forum/showthread.php?p=1262998#post1262998
I hope your PT is working out for you. I have a bit of a pain problem I have to work on myself, but I don't think about it trying to keep the above in mind. Make it work for you.
BTW, your new avatar is absolutely arresting.
If you feel it's hindering objective criticism, I reluctantly suggest a version of the following link.
http://www.jillstanek.com/archives/wicked witch.jpg
Uh, pardon my humor.
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