Supporting institutional fusion research (ITER, MIT tokamak, et al) feels like discretely calculating the sum of the harmonic series: you can keep going for decades, but you'll never get much more than 57.7% (of a viable reactor.)

I'll be excited about the possibilities of usable fusion in my lifetime when SpaceX starts iterating toward a production design.

[0]: https://en.wikipedia.org/wiki/Harmonic_series_(mathematics)