Everything starts with an idea.
These ideas happen at the oddest times in the strangest places. Literally I think of them while in the shower, and even sitting on the toilet! Sometimes it's when I am driving.
Being able to capture those ideas is a critical to moving forward on your thoughts. A friend of mine carries a pocket notebook and a pen every place he goes. When we are at a basketball game, he will take out his pad and pen to scratch ideas down right in the middle of the game. He is usually wearing a sport coat and I think it is probably so he has someplace to put his pen and note pad.
Some people will use voice recorders, most telephones have them built in. You might want to learn how to use the recorder and like my friend, record your thoughts. Obviously, the pen and note pad is much more functional in loud spaces, as well as places that quiet is necessary, such as a library.
When you capture your ideas, you need to be thinking about putting them into action. Sometimes we go back and look at the idea later, thinking that it doesn't sound as good as it did at the time. I would still investigate the viability, because that is most likely self-doubt that is speaking to you.
Remember, you had confidence in the idea when you first thought of it, and now you need to give it a chance. As you begin to research it, your idea will may morph into something slightly different than the original.
The ideas that you have today, might just be the telephone 100 years ago, or televisions being created out of radio parts. Can you imagine if nobody acted on the idea of the automobile? What would the world be like?
Take your ideas and work with them, even if they are far-fetched. They just might be tomorrows reality!