What is truth?

So, what is truth? There are so many different explanations from so many different perspectives, cultures, and beliefs that we could make a mountain out of them.

The Word Net Web defines truth as conformity to reality or actuality.
Buddha said The gift of truth excels all other gifts.
Muslims believe that Allah will lead his followers into truth.
Christ said I am the Way the Truth and the Life.

I'm sure there will be many points of truth that I will touch base on, but right now I am going to start with only a few key concepts.
Today there is a "new concept" of truth that makes me roll my eyes. This statement right here, "What's truth to you is truth for you and what's true to me is truth for me." There are several reasons why I have totally thrown this concept out.

It totally annihilates what has been proven by science. An orange is an orange, and an apple is an apple. If you plant an apple seed, an apple tree will grow. Even if you paint the apples orange, or wrap them up in orange peels, or dump citric juice on them, they are still apples. If someone said, "Well it may be an apple to you but it's an orange to me," I would dismiss that comment as an ignorant assumption or denial. Your personal opinion does not change truth! I may not believe in gravity, saying that it runs against my religious views or personal opinions, but that doesn't mean gravity doesn't exist!
So people would say to this, "Give me a break, I would never try to convince myself to mix up my fruits. This applies to science, but can spiritual things really be proven by science? What about feelings and thoughts? Science can't test those things because they're not physical." True, science cannot test thoughts, feelings, or the soul; they are not tangible. So how do we dictate what is truth about those sort of things?
This is where people start the whole, "If it feels right to me than it must be true for me. And if this feels right to you it must be true for you." And this is where my eyes start to roll. Here's why... You can't dictate truth by feelings because feelings are so misleading! Examples- 1) The murderer felt like killing that person at the time. 2) It felt right to date that person at the time. 3) Today I felt like yelling at my younger brother. See what I'm saying? We can all agree that murder is wrong, most of us would dismiss the murderer as a crooked minded freak that isn't worth considering. So what about example #2? How many people have "gone out" with a significant other, gotten physical, later broken up, and then felt regret or disgust about ever doing that with that person. And then example #3... Yes, my own feelings are also misleading, I was wrong to yell at my brother, in that particular circumstance I could have spoken to him in a regular tone and been much kinder about the issue.
My point is, we all make mistakes, our feelings are not a very good moral compass, everyone makes mistakes based on how they felt at the time. So, if a person believes a particular something for 50 years, lives their life accordingly, and accepts it as truth, is it truth? What if that person suddenly changes their mind and believes something else as truth? What is truth? The first belief? The second? Both? I have an example dialogue below, it's kind of abstract, but work with me here:

Linda: "I believe that when it rains, it means the gods are sad. So when it rains I will stay inside, burn incense, and cry with them. I feel that that must be the explanation for rain, so it must be true."

(And for twenty years Linda follows this practice)

Betsy (Linda's friend) : "Linda, what are you doing inside? Why don't you come puddle jumping with me? Lets play in the rain and have fun!"

Linda: (horrified) "But Betsy! Don't you know that when it rains it's because the gods are sad. They would be angry if we took pleasure in their tears!"

Betsy: "Linda, that's not true at all! I feel that when it rains it is because the gods are happy. They are watering mother earth and causing things to grow bright and beautiful, it's like they're cleaning and gardening their masterpiece! They would be disappointed if we missed out on it! I have felt this way for years, so it must be true!"

Linda: "Why, I believe you're right, what you're saying must be true!"

OK so here's a question, was Linda wrong about her first belief? Or was she wrong about her second belief? They can't have both been right. And both beliefs were dictated by how she felt! Either the gods will take wrath on her for delighting in their tears or be disappointed by her lack of enjoying their work if she switches sides or views.
Time and time again, it has been shown that human feeling cannot always be trusted for suitable guidance. So what are we to dictate truth be? More on that later...