In mathematics it is the symbol of change (the delta), strength (the strongest shape in geometry) and ideal proportions (in equilateral triangles). Architects/builders depend on equilateral triangles in construction because (when made from rigid materials) no matter how much pressure is exerted on all three sides it will never distort, collapse or weaken. It also serves as the symbol for fire and assertiveness.
The long story, short….. for me its strength under immense change and pressure. Staying both passionate and compassionate. Being assertive and taking life by the balls, not sitting around waiting for change but making it. Embracing it all. Staying balanced: in work, in life and in love.