I agree - consistency is the key. If your seam allowances are a little on the plus side then your finished article will be a little smaller and the reverse would be true if your seam allowances were skimpy. If finished size isn't a big issue then strive for consistency. If there are many seams over time a little off will make a difference. If you're 1/8 off in your seam which isn't much but over 8 seams that's an inch which is a big deal.
Are you using a 1/4" foot? That really helps I think. If you don't have a 1/4" foot then use a piece of painters tape to mark a line where the edge of your fabric goes. Even better take a knife and cut down through a roll of painters tape a bit so you get a number of layers already stuck together and then put it on your machine. It will form a dam for you to but your fabric up to. I've also seen people tape an old credit card to the machine as a dam to run the fabric against.
Don't obsess too much. Do the best you can and the more you do the better you will become. This is coming from someone who has point matching OCD.