Technically, past performance is the ONLY indication of future results, for anything ever. You only know that trying to move your finger will actually move your finger because it has worked in the past. You only really know that letting go of your pencil will result in it falling down instead of falling up because of past performance.
Also, "the trend is your friend" is a trading adage for good reason.
Past performance is not a guarantee of future results, but it sure as hell is an indicator. If it weren't, humans would have no way to make sense of the world at all, because nothing would be even remotely predictable; all would be pure chaos. The consistency and regularity of phenomena is the very basis by which one navigates the world and manipulates it to one's benefit.