The truth of the matter is the gadgets really only make up 10-20% of the photo, while the other 80% although may require technical gear is really made up from your actual skills and experience. I am not gonna bullshit you with theories, for this blog is really about my experiences and the opportunity to share them with you all.
I have never felt I shot any better with more than adequate number of equipment and gadgets. Contrastically I always ended up with better shots without what I thought was necessary. The truth of the matter is gadgets/prime lenses/light modifiers sometime not only takes up our time in shoots but makes things more complicated than it really should be.
That's not to say that you should go to your next shoot with nothing but a lens, body, and a speedlite; but if you are often bringing back a lot of unused equipment then perhaps you are overstocking for you shoot.
If you are shooting events...
Bring a good standard zoom and at the most bring an optional ultrawide angle. No need for macro lens or Tele lens. With a lot of good standard zooms lenses the macro mode is adequate enough and if not just bring an extension tube. I like to bring a portable light modifier that is easily storable or easy to setup like the Roundflash. The Roundflash makes a great ringflash, softbox, and it stores away easy without hassle. I can clip the folded Roundflash on my utility belt easily with a small mountain hook and it is never in the way when I am moving around.
For Pre Wedding Photography...
Your basic speedlite (and perhaps an extra backup) with one simple modifier of your choice (something to diffuse most likely) is enough. A lot of people use a boom but for me it's always a lightstand over a boom. Why? Why limit yourself to a boom that cannot stand on it's own when if you use a small lightstand it can also be a boom as well as a standalone stand.
Many people bring reflectors, color checkers, light meters, etc... Sure it looks good for the everyday pedestrian that knows no difference between a DSLR and a mirrorless. The benefits however, of carrying so much extra gear definitely does not weight out the benefits of having a happy assistant.
So next time if you are out on a shoot and you think you resemble this guy
then perhaps it's time to revise how you plan out your shoots.