For years, I wondered if I would ever really like working. My jobs have generally been grinding on me. So far, this one hasn't been. There are frustrations, to be sure. You can't spend your days dealing with smart, opinionated people and not get some friction. But overall, it's pretty nice. And lately, I have been making steps to become more productive.
I can't emphasize what I'm to say next enough: Fight the urge to allow yourself to be interrupted. Context switches are bad for computers, and horrible for humans. Fight them.
Don't be fooled by what constitutes a context switch. It's not just when you switch tasks. It's also when you switch projects. A real problem in a dynamic workplace is the tendency to want to be "instantly reactive". A boss calls for a new thing, and everyone jumps into that thing. That thing you were working on before? He still wants that, too.
Is your boss being unreasonable? Maybe, but probably not. Probably what is happening is that they have identified some problem, and are enthusiastic about fixing it. Don't let that enthusiasm swing the boat wildly. Take a little time and write up a charter for the project, and then ask your boss where it belongs in the priorities. If they are sane, they'll make a cool decision, knowing that their enthusiasm is being acted upon in a real way, and you can then go back and finish what you were working on.
This way, the ideas aren't lost, but the work actually gets done, instead of having thirteen half finished projects that are useful to no-one.
All right, enough blather.