People rarely notice their partner's less attractive peculiarities early on in their life together, because they are so very much in love. However, as the blinding effect of romantic love wears off with time, they become more aware of these disturbing traits, flaws or vices of their partner's. Though founded on love, most relationships rely on good communication skills to get through difficult times, which are bound to occur as the partners spend more and more time together.
In such times understanding the differences between the partners and treating them with patience is of the utmost importance, especially when dealing with trivial things, such as never saying please and thank you, which can be very annoying, but are not worth quarrelling about. However, one can only take so much, so to speak, and this is where communicating enters the scene. At some point, communication skills save most marriages from falling apart, as some chafing between the partners is inevitable, no matter how much in love they are.
Eventually you will have to complain to your husband about his long working hours or to your wife about her affection for shopping and it is best you do it carefully, with a certain amount of diplomacy. Your ability to communicate in a non-aggressive or defensive manner is crucial in doing so, since you need to find an effective way of getting your message through, without offending or angering your lover. Furthermore, being unable to express yourself appropriately (and correspondingly to listen to your partner with understanding) inevitably puts a strain on your relationship, as poor communication prevents you from sorting out disputes, which are then most likely followed by a break-up.
I learned this first hand. While my girlfriend and I were just starting out, we would have a falling-out over the...