I learned to quilt about 2 years ago. I look back at my first table runner (flying geese), which I still use, and chuckle at my inexperience. No big deal - I still use the runner, it looks great and no one else notices. My BFF gave me some sound advice when I was concerned over something that didn't work out quite right recently: She said nobody will be looking at the project as closely as I was.
Here are the things that have really helped for me (and I know I'm echoing what others have said):
I got a 1/4" piecing foot with a guide;
I wash, dry, then starch both sides of my fabric before cutting for a project - the starch really does help a fabric behave. I know it's a pain in the rear end and it's time consuming, but I have noticed a difference in my work since starting this;
Through practice I've learned how to press on the ruler and use the rotary cutter. It's amazing how the smallest thing can affect the cut. I noticed you aren't using a rotary cutter - IMHO you can't get good, straight quilting cuts using scissors. It only takes being off by a hair to really mess things up.
Practice, practice, practice. I think I'm getting pretty darn good at pieceing and getting points to line up (most of the time) and even just a new machine made a difference. I was using the 1/4" piecing foot on the new machine, just like I did on the old machine, and the row of squares came out crooked and 1/2" too short. I pulled it apart, restitched on the old machine and it was perfect. This was a huge wake up call that I need to start all over in practicing 1/4" piecing on my new machine.
In the end my mantra is Practice, Patience and Chocolate. Lots of chocolate.
Good luck... your topper looks really nice and I love the colors.