In The Mythical Man Month Fred Brooks discusses the idea of The Second System Effect. The Second System Effect is the tendency for a project manager or software architect to err on the side of overembellishment when planning their second project. In large part, this is due to the fact that the architect has to exercise a great deal of willpower during the first project by keeping scope under control while constantly thinking about all of the really great things they want to add to the next project. Personally, I think the perils of The Second System Effect can exist well beyond your second project and this is something we always have to be on guard against.
As an architect, your early projects will be like quicksand. They will pull at you in ways that you haven't experienced before and it is important to have an anchor that can keep you grounded and on track. This is why it is imperative that you seek out the mentorship of someone more experienced and smarter than you to help guide you through your early projects. A good project mentor will provide a safe place for you to express your thoughts and ideas about a project and they will give you honest, candid, and sometimes difficult feedback.
If you are relatively new to software architecture or managing software projects, I think that this is an extremely important concept to keep in the back of your mind, even after your second system ships.