Can anyone help me save my beautiful alien plant?

[allhailtheaubergine]

I have a cactussy / succulent sort of plant. Weird, beautiful alien thing; single straight stem with purple and green curling, pointy, fleshy leaves evenly spaced up and down in an almost Christmas tree shape.

It was doing fine outside (I live in the desert), but it was so gorgeous looking that I brought it in, whereupon it shot up a foot in a fortnight. Bright green, straight up, rather leggy, and starting to get too tall and thin for itself.

I put it back outside; immediately all its leaves fell off and it shrivelled and sulked. I brought it back in and neglected it for a month.

I now have a long thin trunky stem with a few wilted leaves halfway up and a little hopeful looking greenery right at the top, which is causing it to bend (top heavy). It's not pretty.

Should I brutally prune it?

Leave it and wait and see?

What?