You are right, most importantly government policies and laws. Many governments don't buy the whole idea of bitcoin reason being that it deflates the value of paper money, so they try to make policies that affects the market. Another point highlighted is appearance of new competitors, that is another pointer, with the way new cryptocurrencies are being injected into the cryptomarket, it wont be long when bitcoin will have serious competitors and that might affect its value. But up on till then bitcoin is still best cryptocurrency