This plant is happy in semi-shade, but will grow best in plenty of indirect light. It is virtually indestructible unless it is exposed to sunlight or dries out.
Signs of weakness
Yellowish leaves: too much direct sunlight
New flowers are green instead of red or pink: too much sunlight
Flowers turn pale green: underwatering or temperature stress
Elongation of leaves: not enough light, or too far away from light source