I have raced Dinghys, Big Boats around closed courses with bouys. I enjoyed it enormously. Distance racing is another thing altogether. You use what you learned around the bouys; this is where you are close to other boats and can tell if what you change is right or wrong. in the Ocean you have to have confidence that your choice is the right one. It is unlikely that there will be another boat against which to measure you choices.
I have raced across the Atlantic 9 times. the video below is the last race I sailed; and the quickest crossing ever; for me. I still smile at the memories evoked by the images. In order to have achieved this crossing we had a number of 300+ mile days.