Being best friends with someone is pretty much like having a job. It's your responsibility to attend in a timely manner, you have to deal with outsiders and their BS, and you have to make sure you are always on top of whats happening around you.
The difference is that you are always expected to be there for them when they need you. You're expected of dealing with them when they are going through a hard time, and you're expected of supporting and making them feel better, and of course, especially when they're having boy/girl troubles.
But what do you do when you've had enough? when you've absolutely had enough of constantly giving advice to your friends that they clearly won't take. When you're tired of listening to the same nonsense over and over again or when you spend so much time with your best friend that you get fed up and need your space! It's frustrating, isn't it? Then, If you start to ignore your friend they continue to annoy you because they made the connection that you're ignoring them. Are you a bad friend for wanting to have your space? No.
Another scenario can be spending too much time with your best friend, who is also your roommate. We must come to the realization that no matter the circumstance, you can't always give your attention to your best friend, you don't always have to be there for them on a daily basis. When you begin to feel this way give your friendship space! Not only will you have a more valuable friendship but you both won't feel too overwhelmed with each other. By giving each other space you won't be losing loyalty. You are taking action for what you need to make your friendship better.