Something where you achieve something and it is robust, such that, you could rebuild if necessary. People often think of it as increasing the current state, which is incomplete. Also incomplete is increasing the potential top state. Part that is left out is increasing the bottom state. I think that you introduce a new (higher) floor that is fairly robust.
Once you learn to walk, for example, now you can open up to do a lot of other things, but you also are unlikely to go back to not knowing how to walk. There is incremental improving, standing, scooting, crawling, but walking is a substantial level up from those.