I think excitement is very helpful and it keeps you motivated.
My approach is, that I allow myself exited, but in this phase I scribble down all ideas and brain dump everything in a trustful place, i. e. note talking app, mind map etc.
After a few days have past I reflect about the ideas and it is so easy because they are written down.
Block some time in your week to work on your ideas. Time blocking in your calendar helps to stay focused and set boundaries when and how long you will work on the project.

Does it make any sense to you?

Good luck and best regards.

Heiko