It is all about gaining experience. You have now learned what not to do! LOL I know you will find a way to make them that suits you and it will all be easy from now on out! HSTs aren't hard! Paying attention to accuracy when you cut and when you join them together is the key to getting good looking HSTs. Always make sure you have a 1/4" seam allowance at the edge when you join two together. If you don't you will lose your points every time!
When I lay one HST face down on another I always make sure they are square and they match each other. If one is bigger or off to the side from the other one then you will have a crooked set of HSTs when you have sewn them together.