You need to learn what difficulty is first and why its important. When I started mining, I had no idea what it was. I just assumed if the price stayed constant I would make the same amount of money everyday.
Difficulty is basically a bad term for newbies. The correct term should be 'Competition ratio'. Basically the amount of coins mined in a day is capped. For ETH its 30000 ETH/day.
Unless there is some network protocol issue this figure will stay constant. So if there is 1 miner, he will receive 30000 ETH a day, if there are 30000 miners all with equal hashrate, each will receive 1 ETH a day.
Hence your enemy isn't only the ETH price, its also the amount of other people that start mining and who's profits you will have to share. In the past, difficulty rarely decreases.
When difficulty increases, it doesn't mean price has to increase. Its a false assumption.
Does this mean you shouldn't mine? No. In fact its highly unlikely you will end up losing money if you start mining. Unless you start a fire and burn all your equipment to the ground.
However for comparison consider this.
RX 470 mining @ 28MH/s ETH today makes ~ $4.63 USD
RX 470 mining @ 28MH/s ETH on March 1 2017 made ~ $1.04 USD
Many thanks for your post, as it gratefully helps in newbies in mining.