If you lose contact with the strongest lift, even in the center of a large thermal, you’ve probably been ejected by the turbulence of its core. When this happens, it usually will push you out the downwind side as your thermal boils up through stronger horizontal winds at higher altitude. New lift rising from the same source will arrive upwind of the position to which you have drifted. In the absence of any other indication, and especially if a climb seems to have slowed with unexpected suddenness, moving upwind will often bring a climb back to life.
Now imagine strong thermals rising through a strong wind. Here we have two types of current colliding at right angles, so there will be significant turbulence. Thermals, therefore, will not have consistent texture or shape. When wind distorts them, a subtle variation of the uniform circle may help to maintain position within their cores. Flying a broad, flat turn on the windward side of each circle and a tight, steep turn on the lee side can offset that tendency to drift downwind from the best lift. This is essentially the same maneuver that power pilots refer to as ‘turns around a point’. Of course such a complication could be overdone, and your thermal lost altogether. Experiment with this, and return to simpler techniques if they seem more effective.