Being imaginative is a great asset. If you are in a creative field then you need an active imagination. However I've found over years that you need some discipline when exercising your imagination.
Anyone gifted with wild imagination can have an exotic idea. From a city floating in the clouds to a man that lives in your bathroom mirror. Our mind is always on the run and it's not hard to think of something unusual just by shuffling a few things in an otherwise mundane thought. You think you have thought of something no one has ever thought before. Then the hubris takes over and the thought remains just that a weird thought. What is it worth?
Any tiny idea like this is not of value until you explore it sufficiently. Branch out your imagination from that first seed of the idea. Push one of the branches as far as you can, then come back and start in another direction. Only when you can develop a sizable world around that initial idea, will it be of value.
For example, as a science fiction writer you can think of an alien planet that has species with three genders and it requires one of each kind to procreate. It's a nice imaginative idea. We generally don't know life forms that require more than two sexes to reproduce. So not everyone thinks of it. But on its own it's just a variation of earthly reproductive system. To make a good scifi novel out of it, you need to imagine the causes and consequences of this kind of reproduction. (Read Asimov’s “The Gods Themselves”).
The same principle is applicable in any creative work.
It's something that I've to remind myself too. Here are few tips that I've found useful.
Make list of all the exotic ideas you get from time to time. Don't flatter yourself too much for the novelty of your idea. Try to develop it as much as you can when it initially comes to the mind. The inital spark is sometimes very strong and you may see a lot of things in that moment of inspiration. Write them down.
Later on go over your list and choose one of the ideas. Then expand on that single idea in every possible direction. You will have to repeat this process again and again, until you come up with something that's deliverable. Many times you need to warm up before you can again start imagining. Reading what you've already written helps you get back in the mood. It gently puts you back into the space that you need to develop.
As an exercise, don’t start with your own idea. Steal it from somewhere else. Then create your own universe around it.
Once you start imagining things, there’s generally no limit. There are so many variables and you can easily get overwhelmed, then you tend to give up in frustration. In such cases it helps to identify some variables of the space and clamp them down. For example, if you are imagining the city of Columbia floating in the clouds, you will have to draw the line when describing the engieering required to build such city. You are not designing a plan to build a floating city, you just need to convince the reader/viewer/player that it's possible. So it might make sense to stop at gigantic zeppeline ships and gas baloons.
It's not important how far away from the norm do you go with your imagination, but how much area do you explore once you are there.