Being confrontational is one of the hardest things that humans have to do. Opening up at the end of the day and letting all of your built-up thoughts and feelings leaves a person feeling one of two ways. The first and most common is the feeling drained and embarrassed as they wish that they could push their words back into their mouth. Or a person has left their heart on their sleeve and has a sense of accomplishment as they carry on with their day as nothing happened. But if you have to come face to face with a friend or partner it is only right to let everything out the first time around.
Friends are tricky. Not knowing when to draw the line when it comes to topics to talk about openly or how many times you can bail on plans before having to apologize for not putting enough effort into the relationship. Yet the hardest thing about having a relationship with any person is figuring out how they need to talk about their feelings and how you should go about responding without acting like a complete asshole.
Some methods that you can follow. You can go to them and ask if everything is okay if you feel as though a vibe has changed. Another way is to wait for them to come to you. In situations that I have been in being the approacher shows your friend or partner that you care and are still fighting for the relationship. Nowadays so many things happen digitally. People would rather text countless paragraphs about how one joke made them angry or send a Snapchat saying that they didn't like that you had someone else on your story. The best thing to do is talk in person. Nearly everything that you are trying to accomplish through texting gets lost in translation. Taking the time to meet up face to face or even over Facetime or Skype is the best way to assess the problem and know how to combat it in the most appropriate fashion.
The next time that you get into a fight with a friend or even start to have ill feelings towards them, getting all of that crap off your chest will not only make your relationship stronger but you will feel better and more comfortable at the end of the day.