Could our brains make us happy forever?

I didnt know how else to state the question but heres what im talking about. I know that when we ingest addictive drugs (nicotine, alcohol, amphetamines, opiates) they all deal with addictive neurotransmitters mainly dopamine in the nucleus accumbens, so what i was wondering is could our brains make enough dopamine to make us constantly happy like the way drugs make you feel? Ive been wondering about this all day so could our brains make us constantly feel the euphoria we get from these drugs? If they cant then why, and if they can why dont they?