What to do when a company/manufacturer, business, etc. doesn't want/need your invention, idea, concepts.

Yes, I know the feeling. I have been doing this now for several years. You will be rejected over and over again by companies that are not interested at all in your inventions. But don't burn your bridges with the company that doesn't want or need your invention, because you might come up with something they are looking for. Maybe it just wasn't the right timing. Maybe it just wasn't the one, period. You can also go to another company, right?