I do not think it is all in the mind friend. I personally PREFER Indica as the way it delivers the effects I need such as anxiety release, pain and it definitely helps me to sleep. While I can obviously take Sativas or hybrids it does react with my body differently. Sometimes a strong sativa will bring on a mild anxiety attack and has actually given me headaches.
I think like modern medicine no one form of it is perfect for all. Due to the unique makeup of our body and it's chemistry; we react to strains differently than one another.
I am a full time Indica smoker. From am to pm it is what helps me function at what I feel is the best balance for my body. It took me a while and little bit of digging into the different strains to figure out what works best for me.