I've seen that syndrome over a hundred times while mentoring and teaching courses and everything can sum up in a single term: Motivation.

The low level of motivation is the reason for you to keep asking that question without taking action.

Lack of motivation is caused by different factors, and could be tackled with different actions. The easiest way to fight that is by leaving yourself no choice.

"Just do it", as a popular brand says in their motto. If you work full-time, quit. All of your income should come from your business venture, so you better get that going ASAP.

If everything is too vague, break it into groups and subtasks. Define everything in details and set milestones. Deadlines are always a good motivator. Announce them publicly to everyone - if you count on your name, you better not fail that.

If you are afraid of the competitors, find your unique selling point. Beat them with a killer feature and sell it at your best.

Whenever my mentees or students have doubts, I outline them the alternative. A boring 9-6 job, a mean manager, tedious tasks, lack of progress. Planning in iterations with pressuring deadlines leaves you no time to think of "can I" since you're too busy to execute the plan and progress further.