It won't ALWAYS be fun! But, don't let those screwups you are bound to make discourage you. Just accept that you are mortal and no matter what you did, someone out here who is flying did it, too. Try to work on it everyday. Tha is really key. And don't be afraid to skip ahead in the construction. If you come to a stopping point on one part (either because you screwed it up and have to order a new part or you are waiting for a good day to prime parts), skip ahead. Do something else. Keep moving. When you get tired of dimpling, move to a different part for a while, then come back later. Play some music you like to make the endless deburring go by a little faster.
When you get frustrated, come here and vent. We will help you out and keep you motivated. But, yeah, it is mostly fun. I have even found myself wondering what I will want to build next.