Place a block of Obsidian above your head to minimize taking massive knockback from your own TNT.
To help you get the best "piece" (or technique) for your situation, are you working on: to mid? Vertical jumps to reach high bridges? Defensive or counter-offensive jumps in a tight spot? TNT Jump
Practice placing the TNT while running forward, aiming for a consistent jump-run-place rhythm to avoid falling into your own trap. 4. Advanced/Creative Methods Place a block of Obsidian above your head