HI. Number one on the list is the dreaded 'tweezer launch' that we never, ever, no matter how many models any of us build, seem to be able to work out of. Luckily in the last couple I've been building, even through I've dropped several parts on the floor, I have been able to find them. Of course, working out in the garage on a cement floor does have it's advantages in this department.
One good solution for those who work inside is putting down the simulated hard wood flooring in your room. This would have to be better than carpeting. Might be worth the time and money spent to put it in. Not that hard to do, except on the knees and hips. But this is an age thing.
Number two is painting. I'm easily frustrated when my stuff doesn't turn out like some of the very fine models I see on this and other sites and magazines. I know that the only cure for this is practice, practice, and more practice, and I am getting better, very slowly, but it still can be frustrating.
But when a model does come out that I can say I'm basically happy with the end results, I feel that I've really accomplished something positive and have learned a tad bit more about a particular vehicle and the time period it was used in, which is kind of one of the reasons I got involved with modeling AFVs in the first place.
Take care, sgirty