That's why most painters drink to much. In the morning there hands shake and it's time to cut in.
The trick is to use a top quaility brush like a Purdy or Wooster brand brush. It holds more paint and leave less brush marks.
I think the use of undersized painting tools is probably the single most popular mistake DIYers make. I have a couple of nice 1" sash brushes but through the years I only use such things when I just cannot fit something else in a space. The edge of a nicely trimmed 2.5 or even 3" angled (my preference) sash brush will almost do pinstriping once you get the hang of it. Little brushes just do not hold enough paint. I can fly through, for example, a chair rail with a 2.5 angeled sash brush. A one incher would take forever and the result would look awful.
Same thing with knives for patching. A nice wide drywall knife will blend in patches better because it can use the wall surface to provide level to the patch. Saves sanding in the long run. I never use a small putty knife even for little picture frame hook holes.
And don't buy roller covers that are two thin. I used 3/8 or 1/2 nap minimum when applying decent paint.