Happiness Questions

So as I am going along here more and more I start to have questions that I can't seem to find answers to.  Hopefully I will find these answers eventually but if anyone has any wisdom to share I am all ears. Here are my questions.

1. I have heard that anxiety can exacerbated by thinking errors.  This has made me wonder how much of Cognitive Distortion leads to unhappiness?  How much happiness do we really control in our minds?  How much of our own happiness can be destroyed with our own thoughts?  Are these learned behaviors?  Are they a product of our mood or mindset?

2.  Along with the questions above, how much of our happiness hinges on our ability to see and believe in limitless possibilities?  Obviously our belief in possibilities leads us to act and if we believe in nothing we are hopeless and we are in a position to do nothing about it.  My coworkers were talking today about all the school shootings going on now and they were saying people who get in those situations see it as their only option.  It has made me think of myself and how narrow minded I can be when I consider the things that will make me happy in life.  Are there many other possibilities that I have ruled out unnecessarily just because my brain isn't creative enough to think of other options?  Are there new experiences that I could be enjoying right now that I have somehow ruled out in my mind and I am standing in my own way?

3. How much of diet affects your levels of happiness.  Obviously your body has nutritional needs and when they aren't being met we can all get irritable but does this also connect with our overall happiness and if so how?

4.  My last question seems to be a simple enough one but I have yet to see or find any studies that prove my thoughts either way.  The question is, when we serve other people does it matter if our service is noticed, recognized, appreciated, or rejected?  Obviously the Savior healed all 10 lepers even though only one of them showed gratitude so I am not suggesting that we should only serve people when we receive praise, recognition, acknowledgement or gratitude, but how does all of that affect our happiness and does it have to?  Can I be just as happy doing service for a person who slams the door in my face as I am serving someone who is incredibly grateful?

Like I said these are my questions and if you have any thoughts or can site any studies I would be happy to hear what you have.  In the mean time I will keep searching. Thanks friends!