To build on this theory;
We currently see the FTSE 100 market (daily chart) that the Rate of Change is above the zero value line and still ascending implying a rally to continue BUT the rate of expansion of the trading range is declining. Thus a close below yesterdays trading high would suggest imminent profit taking so bulls beware imho.
Chart attached to show prior incidences.
NOTE the ROC must be in positive territory for this strategy and ascending.
Normally this also works with the major fx pairings too :-)