Reddit mentions of When I Say No, I Feel Guilty: How to Cope--Using the Skills of Systematic Assertive Therapy

If you just want to vent you can use r/offmychest or r/rant. But it sounds like you wanted some feedback and I'm a wordy guy so... :)

If you've watched shows like Top Chef, when the contestants have to collaborate is when the most sparks fly. Trying to get a group of people to agree on one approach is extremely difficult. That's when passions really flare up and people get emotional. Many twists and turns, disagreements and last minute decisions are the standard, not the exception.

So realize you are in a tough challenge. But also realize - that's the point of the challenge. Can you get along with the others, help execute what they want to do, but also not lose your own voice. You want to have something in it that is quintessentially you. You want the teacher to be able to say, "yes, I see your contribution."

Video editing is a big deal. It's one of the core processes that result in the final product. So keep notes on how everything is going. Where are the rough patches in your efforts to collaborate. Don't disregard what works well. Make a note of that also. Even accentuate it if you can. Finding what works and putting a spotlight on it makes everyone feel better.

Keep your disagreements one-on-one. Negotiate individually when a conversation turns into a conflict. Don't talk bad about people to others. Don't gossip with people you know can't keep a secret. Don't complain to the group about one person. Work on being concise but eloquent and patient under pressure. This is a huge part of any stressful job and the better you get at it the more it will result in promotions and more interesting projects. If someone ever offers to fly you out to work with a team on a special project, you will know you have made it. Take it!

The director for your team project wants to have a say in the audio assets. That's fine. As Editor you have the ability to finesse the placement of the audio. Make it a collaboration between you and the director. Director is like the executive chef. They have final say over every dish before it goes out of the kitchen. If they say "no, no good" ask for specific, explicit instructions on what they want changed. If they don't know or can't explain, offer recommendations on what can be done differently. That's where your opportunity to shine is. Make notes of what you know are your contribution to the final product so you can tell other students and especially explain to the teacher what your role and contribution is.

You have to admit, since it's a video short, you might not want the music to be too complicated. But you can also create an alternate version and present it to the director. It takes extra time of course, your personal time. But if they still say no, take it in stride and do what the director wants. It's your job to execute their vision. That's where you can disengage from anger and frustration. Just like you said, you're not the director. So don't let a crappy decision ruin your day. You'll have more choice and control in later projects. Use this to remind you to look for opportunities to work with people who appreciate your input.

Some directors are going to suck! Some are going to be really terrible to work with. It will either be because they are completely inept, frustratingly mediocre or because they are actually a genius. Give them time to reveal which they are. And at the end, try to preserve the relationship, even if you don't intend to work with them again. Learning how to execute what they want is where your skills can really grow. Turning a vision into reality is not easy, so that's where your skill and creativity can be found. Always learning, practicing and experimenting.

In an industry like film, you want to protect your name. You want to be known as a person who is great to work with. Easy going, flexible, resourceful and hard working. That's more important than winning every little decision that has to be made. That's why there are so many books like Difficult Conversations and When I Say No I feel Guilty to help people improve their communication, listening and assertiveness skills. Hang in there and good luck!

[edits: spelling and for clarity]