Developing great mental health is one of the most important personal responsibilities. It's no different than developing great physical health. You can learn techniques and best practices, and if you practice them with consistency, you get great results. Here are some things that have worked for me in creating a state of mind that is peaceful and allows for easy joy. Not only is there a general sense of ease in this state, but there is more room for creativity and ambition, because there's less fear and self-doubt to stand in the way.
Realize that "problems" are an invention of the mind
Any problem has been invented by your mind. "Problem" is a simply a label that your mind has applied to a given set of conditions.
It most likely did this because there is something you desire that this set of conditions is keeping you from. You have to either give up the desire, or at least give up the problem label. This is the single most important technique I've found for living well.
Put care into your environment
Keep your environment clean. The practice of putting care into you environment is an exercise in itself. Your environment becomes a reflection of your mind, and your mind becomes a reflection of your environment. Messy mind = messy environment. Messy environment = messy mind.
Sit. Just Sit
Meditate. Don't know how? Just sit. But what breathing technique should I use? Just sit. What posture should I use? Just sit. Eyes open or closed? Just sit.
If you want more instructions and want to develop a more disciplined practice, you can do that. I personally use the Zen technique of Zazen. But forget about technique, just sit.
It's all you need. 20 minutes a day.
One thing: observe your thoughts. When you get lost in thought, label it "thinking". That's all. The goal is not to think of nothing, that's a misconception. There is no goal.
Your mind will do all kinds of crazy things, and that's perfectly fine. That's part of the exercise. You just sit, and when your mind starts chewing on itself, just notice it and label it "thinking". Don't achieve enlightenment. Don't achieve anything. Just sit.
Get Out Of Your Comfort Zone
Do something that scares you. It can be anything, big or small. Tell someone how you really feel, go skydiving, do something you're bad at, try a strange food. It doesn't matter. Just do it and feel good about yourself.
There's not much to be truly afraid of. Most things can't kill you, and if they do, well that's nothing to be afraid of either. It's a guarantee my friend.
The more you embrace this way of thinking, the more free you become.
Be Forgiving Of Yourself And Others
We're all doing our best, and we all deserve respect and love. Listen to others with your full attention, and appreciate them. Don't "make them feel appreciated", just appreciate them. Be patient with others and realize they have worries and insecurities just like you. When we see that these things are universal, it's all good. We see each other for how we are and we accept each other. When we accept ourselves, it becomes easier to accept others. And when we accept others, it becomes easier to accept ourselves.
When you eat, take some time to think about where your food came from. It doesn't matter if it's an apple or a Big Mac. Before you take a bite, sit there are and play a mental movie of every step in the process of how this food arrived in front of you.
For example, imagine the apple as a seed, then growing into a tree. Imagine the apple in its beginning stages growing on the branches of the tree. Imagine the rainy days and sunny days that came and went and contributed to its growth. Imagine the person that picked the apple. Imagine their family and their kids' reaction when they get home from work. Imagine someone sitting at a computer designing the graphic that goes on the sticker that goes on the apple.
Imagine the apple sitting on a truck and traveling for miles on open highway on the way to a distribution center. Imagine the truck driver. Imagine the apple being placed on the shelf at the grocery store. Imagine all the people who stopped by this shelf to pick up an apple, but didn't pick this one that sits in front of you. Imagine yourself coming by and picking up this exact apple. Now take a bite. You're chewing that entire process. That entire process continues in your body and actually becomes part of your physical body. An apple isn't just an apple, its a process. An unfolding chain of events. A culmination of infinite variables.
It's a lot to go through if you just want an apple, but if you do this when you eat, it becomes very difficult to see yourself as separate from the incredible chain of cause and effect of the world that you are a part of.