Start by playing maps with a spacing big enough to get follow points appear between each hit. When you just start playing HR you will be using follow points for real for the first time in your osu! life, they really help A LOT when you just begin. You'll notice this after a few hours/days of practice, if you play any map where you don't really get follow points because the spacing is too small, you gonna have a lot of trouble reading the map.
It may take time to "warm up" your reading skills too, for example, I find it very hard to read AR 10 when I just start playing (since I'm not really active at all), but after a few minutes I can play it normally. So yeah if today you are doing GREAT after a practice and tomorrow you suck, it's normal.