Was it hard to come up with the idea and believe in it enough to pursuit it to where you are today? I think self doubt must be a challenge, especially when you

Was it hard to come up with the idea and believe in it enough to pursuit it to where you are today? I think self doubt must be a challenge, especially when you are alone and still far from a proven concept and nothing so show to customers. Was this idea the only one you evaluated before you chose it or did you also have other ideas, of which this one you liked best?