This question of mine is actually philosophical. Way back in college, I remember we were discussing in a philosophy class two schools of though - rationalism and experientialism. To put it simply, the former claims a person have in himself an INNATE knowledge whihch is developed by way of thinking, reasoning, and rationalizing things. The latter disagrees and tells that without experience (through senses/emotions), there can be NO knowledge of something. Thus, the issue is where do we really LEARN from - from knowledge or experience?
In my analysis, when it comes to sensory things such as accidentally pricking your fingers with needle while sewing, experience comes first before you would think that you have indeed accidentally pricked yourself.
But for emotional matters such as your mood, temper, and feelings, I think it's more influenced by our personal mental outlook or vision in life in general. Yes, bad tempers can be caused by physical reasons (such as sickness) but you see, let's face it - we almost don't notice it but sometimes, we're simply CREATING, through our mind, our emotions or the emotions that we want us to feel or we want to project to others! This is where fields like Psychiatry deals with where it aims to change and alter negative expeirences (emotions/feelings) through rationalizing (thinking/reasoning). (This is why there are quotes such as "Fear is all in your mind" and fear is a kind of mood/emotion.)
You see, so far, I somewhat concluded that a person's mind/thinking/reasoning/understanding can change emotions/feelings/moods/experience - not in reality, but at least in the level of the mind - VIRTUAL. If you want the realistic level, simply do the other way around which is common - when experiences turn from bad to good, of course, the natural mental response is positive.
But the only thing which seems, for me, that the mind CANNOT (or very seldom) change/dicatate/alter is the experience of LOVE. But this is still debatable - how are we attracted to somebody we love - through thinking or feeling?