Psychological: you feel good, you have energy, positive outlook on life, you sleep well
Physical: breast growth, female fat distribution, less body hair/slower growth, less/no body odor, facial changes, skin less oily, softer/translucent, overall feminization
Signs of too little may include anxiety/depression, trouble concentrating/brain fog, hot flashes, night sweats, feeling very tired/unmotivated, memory problems, overall health deteriorating, bone loss, ageing faster than normal, etc.