Sometimes I get drowned by my imagination. I'll give an example. An hour ago I was reading some stuff about esoteric programming languages. Then my imagination kicked in. After that I was just sitting for an hour and drawing in my head a nonsense visual programming language. Useless stuff, I hate it, I am practical person. Rarely, but sometimes I hook on an idea which has a practical value. Then it is even worse because it is even harder to stop thinking about it. The problem is that I get over-excited during such moments and it is hard to pull away myself from delusions. I think my imagination works counter-productive for me. Any thoughts how to fight the temporary over-excitement?
Don't you control your focus? Perhaps you have to find a way to recognize what you do control and assert that power. For example, if someone tells you, "Don't think about X," then chances are that you will be thinking about X pretty much right away. Is that a bad thing? Probably not but there is some self-control that likely has to get some practice as well as finding various coping techniques as you could use some Cognitive Behavior Therapy if you want a phrase to Google about this. There may also be something to figuring out why you like going on such flights of fancy to have your imagination go to such extremes. Perhaps you see it as a muscle that has to be exercised regularly to maintain its power and strength. Chances are that there is some payoff for you in some way here though you may not like seeing it or admitting it. You could also look at Emotional Intelligence tools for self-awareness and self-management for another idea.
Something to remember is that you will probably end up building a toolbox of many different strategies and techniques where quite often some will fail yet they may work at other times. Building up some tenacity to keep trying things, keep score on what works and doesn't work, and analyze to see what patterns emerge. Mindfulness would be another idea to toss out there, where there are various meditations and other practices you could use here for another way to just be present and not worry about the future or dwell too much on the past.
I found it useful to have a folder of idea documents and put my thoughts into them. As they get committed to paper/file, they leave my head.
Some of those ideas I come back to later from different angles. I then add to those files.
After a couple of years of doing that, I have two potential startup ideas with technology, business and human aspects thought out. Plus another 20 or 30 or random semi-written things. What is interesting to me is that some of the semi-written things other people built startups around. To me, it is validation of my thinking process.
This fits together with GTD with using the capture tools for everything and then finding place for it (filing/someday-maybe in this case). Otherwise, the same thought will keep coming back and wasting your energy.