If you do the research before you introduce anything into your tank, I think you'll find it not that difficult. Just takes time, money and patience.
There are many variables involved, but the main things you need for successful coral growth is very high lighting levels, high water movement (powerheads), excellent water parameters and occasionally you'll have to replace trace elements that have been used up or removed via the protein
skimmer. The excellent water parameters comes from frequent testing, frequent water changes, copious amounts of
live rock, low nutrient load (few or no fish), etc.
Some fish species do indeed pick at various corals and invertebrates, which is why you need to reseach all inhabitants before introduction. These fish are usually deemed "not reef safe".
To me, a nicely set-up reef tank is the ultimate accomplishment in this hobby. You need a lot of funds to get one setup and running. The equipment - lighting, skimmer, live rock etc. can get ridiculously expensive. The corals, fish and inverts cost some serious jack too.