Nobody's perfect. Things can be going beautifully, and all of a sudden become very messy. Not everything is going to go over smoothly, but that's expected. People get stressed, and they overreact. How you handle these situations is what truly matters.
I've seen it all. I've seen people leave these occurrences behind them and move on with their lives as normal, picking up right where they'd left off. I've seen people bottle their emotions in, and not communicate their feelings. I've seen people communicate their feelings to others, but not reach out to the person they're actually upset with in order to resolve a problem. I've seen people be outright nasty for no reason. I've seen people act quite maturely, but I've also seen people act in ways I thought only occurred in middle school.
I'm the type of person who faces things head-on. If I'm upset about something involving someone, he/she will hear it directly from me. I don't like leaving issues to brew, so I tend to directly confront people. That's not exactly everyone's prerogative, but hey - they're not me. Everyone handles their situations differently... some haven't exactly made the choices I would make, but hey - I'm not them.
Some find success in being more passive. But this has two different outcomes - either it gets dropped completely, or it brews. The first is an easy way for everyone to move on. The latter is a disaster waiting to happen. If you feel like something is only gaining steam, then ignoring the issue may not be the best idea. That balloon will eventually burst, and the result will not be pretty. At all.
In resolving an issue, you may just have to take a second and think about whether or not it's actually worth drawing out. If the issue doesn't actually pertain to you, drop it. I cannot stress that enough. If you were not directly involved in something, you have absolutely no place to judge. The best idea, in this case, would be to just accept the fact that things don't always go the way you want them to.
They don't always go as planned, either. If this involves a friend, think about how important that friendship is to you, and whether or not drawing things out that don't involve you is worth risking that friendship. Honestly, actually drawing it out will not only make you look immature but may also come across as you questioning your friend's character... and believe me - that is not worth it. You choose who you surround yourself with, and you chose these people for a reason. Remember that.
These things are going to happen. There are going to be rough patches. There are going to be things that people do that you don't always like and/or agree with. There are going to be things that happen that you can't wrap your head around. But at the end of the day, it's the way you handle it that people will remember.
If you messed up, own up to it. I know - much easier said than done. But taking responsibility will maintain the respect others have for you and will keep your maturity and integrity intact. If someone takes responsibility, don't draw it out. Trust me - it's not worth it. That will only dig the hole deeper, and then you're in an even rougher patch that will be even more difficult to work through.
Not everyone operates the same way. This is to be taken into account for not only what you're handling, but also the way things are handled. People aren't always going to do things you would necessarily do, and they won't always handle it the way you might've chosen to. It takes a lot of acceptance, open-mindedness, forgiveness, and patience. Much easier said than done, but definitely more worthwhile in the end.