I can, and I'm going to talk about one of my favorite things: food. I'm going to lay out my philosophy for having a healthy diet, which is remarkably like my philosophy for having a happy life, and I'll even explain why at the end.
1. Know your limitations. This may seem like a downer of a way to start, but when you're looking at building a healthy diet, the first thing you have to do is figure out where to say an absolute 'no' to yourself. Are you allergic to any foods? Do you have any sensitivities, or any conditions like Celiac Disease or lactose intolerance? Cut out the things that damage you, that should be nourishing you but are attacking you instead. For now, whether you 'should' do certain things is irrelevant, 'dietary guidelines' are irrelevant. Simply try to identify all the things that actively harm or poison you, and cut them out of your life. I, for example, cannot have artificial sweeteners; they give me migraines. Rather than lamenting my inability to have something most people can have without trouble, I accept that I have a non-negotiable hard boundary that limits me in some small way. I incorporate that boundary (and a few others) at the foundation of every meal I build and every set of decisions I make about food. It's part of who I am.
2. Know your history. Do you have any addictions? Any relationship with certain types of food you feel you don't control? A fear of trying new things? Do you have a condition like diabetes or high blood pressure, that affects the choices you need to make about food? Did your family express love through certain types of foods? Did your family instill certain 'food rules' in you? Where, simply put, do the attitudes you manifest come from? My mother instilled in me at an early age that it's not dinner unless there is a green vegetable included. I've been able to expand this to things like squash, but if I try to eat just meat and potatoes for dinner, I feel unfulfilled because my internal expectations for 'dinner' haven't been fulfilled, no matter how much I eat. Learning to acknowledge my expectations and determine whether they're reasonable has been one of the most empowering things in my entire life.
3. Really understand your goals -- and the goals behind them. If you ask someone, "Why do you want to lose weight?" you could get back a variety of answers: to be healthier, to be more attractive, to feel better about myself, my doctor says I have to, I have a really kickass dress my butt is just too wide for...the list is endless. Sometimes, though, the answer really is, "Because I think I'm supposed to want that." When you set goals, especially goals based around something as necessary as food, drill down through those goals until you really get to the heart of what motivates you, and make sure that what's motivating you is not, in fact, a set of expectations someone else chose for you.
4. Make sure your choices are feeding your goals. If you want to gain or lose weight, if you want to completely change your diet, if you want to become a locavore, if you want to raise your own food, you're going to have to make months, maybe years, of small, sustained choices that lead you to the goal in incremental steps. If you believe that eating a certain way (paleo, organic, vegan) will bring you a set of benefits you want, then regularly check in with your habits *and* how you're feeling. Every so often, step back and make sure that your choices are pointing at where you want to be. If they're not, then either the choices need to change or the goal should be revised.
5. Will is strong, but so is Science. If you really really want to subsist on nothing but bacon and vodka, you will get scurvy and eventually die, no matter how much you believe that's a sustainable diet. It is theoretically possible, through skilled and powerful application of tremendous Will, to bring almost anything to pass -- but if you have that sort of skill and power, why use it to change the molecular makeup of bacon to include Vitamin C when you could just drink a glass of OJ instead, and have all that energy for something else? If you can use science and reason to your advantage, your Will can achieve more than if you try to fight them. If, for example, I know that eating high-protein cinnamon-chocolate multi-grain oatmeal will keep me feeling full twice as long as the same number of donut calories, or that certain vitamins improve my absorption and use of other nutrients, then I can use the science to boost the power of my choices.
6. Listen to your cravings. Once you really start focusing on feeding yourself what you need, and paying attention to what you put into your body and bring into your life, you'll find you have a lot sharper awareness of what you want. Generally, even the 'bad' cravings (the ones out of line with your goals) tell you something important, and you can train your body to respond to a need for iron and protein by telling you "I could murder a good steak" instead of "I need a Big Mac." If you're willing to listen, you will generally tell yourself what you need, and how best to nourish yourself.
7. Don't eat anything that isn't delicious. This sounds like a stupid rule, but there are so many ways to have good, tasty, healthy, nourishing food that you should never say to yourself, "It tastes like shit, but it's good for me." There is no 'good' food and no 'bad' food. There is "Food that will help get me where I want to be" and "Food that will get in my way." Never choose penance when there are joyful options.
8. Make sure you know what you're feeding. Some things feed your body. Others feed your mind. Others feed your spirit. Ice cream may be a good source of calcium and dairy protein, but I eat it because I love it and it makes my soul happy. You should not eat anything that doesn't nourish you, but different things will nourish you for different reasons, and once you manage to work out your cravings and listening to your needs, you'll be able to understand what to feed, and when.
Now, it should be fairly obvious how I apply these to both diet and life. If you start from a position of knowing what it's just not reasonable for you to expect of yourself, and build yourself attainable goals that meet *your* needs, then you start to build healthy practices in focusing your energy where it'll bring you the most joy. If you shift your life so that everything you bring into it feeds you somehow, nourishes or supports you somehow, then your path becomes much clearer. And if you make it your daily practice to choose the joyful, nourishing, fulfilling options, you may not ever be completely free of unpleasant obligations, but they'll hold a much smaller space in your heart.
You'll notice there are no details here. No "always eat organic" or "never eat processed sugary snacks." That's because there's a different path to health and happiness for each of us, and we have to choose how we'll find it ourselves. What works brilliantly for me might be poison for my friend, and you can't judge the success of your journey by how well you walk the best path for someone else.