Take the time to define your project. Check with all the project customers or stakeholders. Verify they understand what you’ll give them and when. Make sure their expectations are the same as yours.
This verification applies to the project sponsors or underwriters as well. Only when you’ve defined your project should you begin detailed design.
It’ll be tough to resist both the natural impulse and the external pressure to push your project along, but resist it you must. Spend the time now, so you don’t have to spend much more time later. Think of it as an investment. You’re investing in your future.