I'm a completer-finisher and I work with lots of ideas/ starter people - they can do things that I'm really not brilliant at so I really respect your skills OP. Don't be downhearted, and I love what pp said about it's a preference.
I also do lots of helping my colleagues.
I tend to work like this:
Write down what I want to achieve in the day. It might include parts of tasks (e.g. the next step of a big piece of work).
Decide an order, 1, 2, 3
The order will include the scheduled aspects of the day like meetings. It might have time limits, e.g. no. 3, as far as I can get on that task before the meeting at 12pm
no. 4 meeting
no.5 next task
Start task 1, Don't get distracted, don't worry about any of the other tasks, focus and finish it.
On to task 2 etc...
Take coffee breaks between tasks. Or, between tasks can be the time you check emails and do any quick helping colleagues stuff as light relief. But any larger piece of helping or email has to become a task with a number in the list, possibly even on the list of another day.
That's my mindset that helps me.
This relies on setting yourself tasks that are small enough - so it could even be
- write the paragraph about risks
- write the paragraph about funding
- check report for spelling... etc
etc rather than 1. write report (too daunting, you'll just find excuses to do something different instead)
Also on big tasks I plan ahead and get meetings in people's diaries ahead of time e.g.
Sept - book venue
Oct - book meetings to discuss event aims
Nov - look at facilitators ideas
- book meetings to agree schedule
- book meetings to commission briefing papers
Dec - compile briefing papers
Jan - send participants final event details
I do this to give myself the confidence that the overall task will get done. Then I'll know whether and why tasks to move that along need to be on the list of any particular day