Expression for a situation where you are too used to your work that you don't see its beauty/potential

Perhaps you would describe this situation as you can't see the forest for the trees. (dictionary.com)

An expression used of someone who is too involved in the details of a problem to look at the situation as a whole

This expression does have a bit of a negative connotation, but I think in this case it's not too negative for what you've described.

You've plainly become insensible to the beauty and uniqueness of your creation (sense 3):

3. unaware; unconscious; inappreciative: We are not insensible of your kindness.

A few possibilities spring to mind:

• objectivize: To make objective or impersonal; objectify

Your first production mobile app is something you have objectivized, at least for the time being, since you are in the process of bringing it into being. Naturally, you need to step back and ask questions such as, How can I improve it?; What is wrong with it?; and Is the cost of making it available prohibitive?

• to take for granted: to underestimate the value of: a publisher who took the editors for granted.

To take something (or someone) for granted means in your case that you are temporarily underestimating the value of your mobile app until you consider it a viable and sellable commodity (in other words, ready for the marketplace).

• to become habituated: the process by which one becomes accustomed by frequent repetition or prolonged exposure.

Habituation need not necessarily be a bad thing. Habituation causes you to see and do things over and over again--as with the application of the scientific method to some undertaking, for example--so as to keep your feelings, which can often prove distracting and unproductive, in check.

• to become oblivious to: lacking conscious awareness; unmindful: oblivious to her surroundings; oblivious of the criticism against him

I insert this word as a possibility, since you seem to lack conscious awareness of the felicities surrounding this "app" you're currently working on. True enough, some developers or inventors become enamored with their app much too soon. Consequently they find objectivity vis a vis their "baby" difficult to assume. In your case, however, you seem to be keeping your distance from subjectivity and pride in your accomplishments until you've finished your masterpiece.

you are jaded. Merriam-Webster

2. made dull, apathetic, or cynical by experience or by having or seeing too much of something

Example (made up):

After four weeks in the Seychelles, I was jaded and oblivious to its extreme beauty; the real world was an enormous shock when I returned to it.

If you have to go back to an earlier version of your app, you will be in shock too.

I couldn't readily find a reference for it, but what you're looking for may be too close to see it and variants. You need other sets of eyes to help you see what you have lost the ability to see by virtue of being too invested in something or having been over the same ground too many times. I have used and heard this term often in connection with the development of documents, which are analogous to your UIs. Getting external feedback early and often, long before you lose the ability to see whatever it is you're producing, is key to success.