Don't worry about "long straight lines". I have been doing SITD for 6 years and my lines are still not straight!! It's all part of it being a handmade quilt. No one but a computer machine or a longarmer with a long straight edge can do a perfectly straight line.
Just enjoy the process. Whoever gets the quilt will never look at it and say "My, but her lines are all over the place!" LOL As if!!!! :-)