Interesting post. The various responses also useful, so this is just another perspective.
The three scenarios you outlined (promoting new venture; practicing guitar; and exercise) prompt a question.
Q: Who is it that has the resistance? I'm seeing three different areas of focus.
Q: Who is being held responsible for the outcome for each area of focus?
In other words, tap into the 20K foot Areas of Focus and Responsibility and fill it out respectively.
In the business venture, maybe the Natural Planning Model is a good starting point. This is a powerful GTD tool that will dynamically morph and benefit as time goes on and will shape how the world receives your venture, including the bank who will ask for a "Business Plan".
I'm not that musically savvy, but I understanding "gigging" to be actually performing live in front of people, who possibly paid to be there. Putting on a great performance, delighting the patrons, and being asked back by management doesn't happen when you don't first practice your craft before the limelight is turned on.
Exercise. That's a good one. Who ultimately is held responsible for your health maintenance and preventive healthcare?
I think you opened the door when you said, "I really felt motivated to practice guitar more when I agreed to start gigging!". Q: Who agreed? What was the underlying thinking there? -- somewhere, I believe, was a thought of immediate personal responsibility towards a future live event.
Hook me up with tickets when you play Ventura, CA.
I encounter a lot of resistance in myself when doing activities where I won't see any real impact for a while (even thought I know it will benefit me long term). Some examples are: promoting a new venture, practicing guitar, exercise etc.
I'm trying to think more strategically about overcoming this kind of resistance. It's not a question of GTD practicalities (I've got appropriate reminders etc), it's more a motivation question for me. The two tricks that I've found most helpful are:
1. to try and give myself as much data to use as feedback about the process, even though no "outcome" will arrive for some time. For example, tracking my own sales activity helped me overcome the resistance to selling.
2. Committing myself to others as a motivation. For example, I really felt motivated to practice guitar more when I agreed to start gigging!
I'd be interested to hear others' experiences of meeting internal resistance... How do you overcome it?