Ideas are like plants, just like plants when you plant a seed (a viable seed) and waters it coupled with the rain and morning dew with the Sun it converts all of these resources into its food which makes it to grow and further in time produces fruits and more generations.
So it is for our ideas, when you let out your ideas to be watered by rain and Sun ( that is taking actions ) it may die or get transmitted into another's mind. Most times ideas that we have are not just only in our heads they are like the wind if another mind or minds felt it they may quickly take actions and you end up saying “and I have thought of this before”.
Don’t be the guy saying “and I have thought of this before” rather be the guy saying “let me show you how I came about it” from press conferences and interviews.
Do not let your idea stay idle, start from where you are.