How to discipline yourself while working alone?

Set daily/weekly/monthly (Each one) goals and reward yourself for meeting and exceeding goals.

Short terms goals and willing to make them real will push you everyday.

Electrodes wired to sensitive bits, and a shockbox with a momentary switch sitting on the desk beside the keyboard, for convenience while working. Break out the whips and sticks for short "refresher" breaks and a quick workout and stretch.

Reserve the scourge for when you really need to get the blood flowing and regain intensity.