Sometimes the desire is just a matter of achieving momentum. I've let my hobby desk collect dust (figuratively speaking; my OCD wouldn't allow it) until I come across something that piques my interest and I plug in Ye Olde soldering iron and fiddle around. Might do that a few days, fall into a lull and then suddenly pick up and follow through.

My knowledge in that area (and software) gives me the leverage to make cheap-but-adequate tools that would cost $15-50k or more from watchmaker tooling companies.

[1] Basically, using my annual watch "budget" to buy a watch that had some unique or unusual attribute, not really collecting in the traditional sense.