Should You Collaborate? (yes)

The best projects and products are almost invariably collaborative.

Do not underestimate the importance of making money. Your quality of life, your life expectancy, chance for a successful marriage, and chance of retirement all statistically depend on making money with what you do for a living. Some considerations with that in mind, then, with regard to collaboration.  

Portfolio 

The worst mistake you can make is thinking that the best things you can create are things made on your own, from your own mind and vision. Some people just don't think themselves good enough to collaborate early on. These are false assumptions. The best projects and products are almost invariably collaborative. Perhaps there's one primary driving force behind a project, but even then it's collaborative and you probably aren't that person, unless you're already highly experienced. The best thing you can do is involve yourself in good projects with good teams, and try to be a valuable and productive member of that team. You'll build a portfolio of much more impressive work than you could have by yourself. Are you taking credit for stuff you didn't do? Not really, but it does reflect well on you, and most employers want to know you work well with others.  

An experienced dev won't let you skate if you give him something he can't use

Learning to Contribute 

Almost more important than the portfolio aspect of collaboration is the growth and learning aspect. On small teams you will be learning how an artist fits into the overall process of development. You'll learn what the expectations are for deliverables and for design work. The smaller the team, the more things you'll be responsible for, but either way you'll have to learn what the developers need to work with. You'll quickly run up against the limitations of different programs, methodologies, and file formats. You would not learn these nearly as quickly if you're doing everything yourself, because you're likely at similar levels of experience in the various disciplines. An experienced dev won't let you skate if you give him something he can't use, whereas you might try to find a workaround. Each team member is responsible for knowing best practices in his area. 

There's a lot to know, and you won't if you don't work with others. 

Speaking Human 

You'll also grow to understand how to express yourself to different types of people, and to understand what they're telling you in response. Everyone's brains work differently, which is one of the best aspects of life on this planet. That means, however, that language can be an issue between people who think very differently. Part of this is because the concerns of different people are so different. Working in a group will help you understand their concerns and perspectives.  

In fact, I would argue that after the project manager, it's the most important that the designer understand everyone's role. The reason is that you will be making sure what you design is A) doable, B) able to fulfill all the requirements, and C) not going to make everyone hate you. It goes beyond concerns though, because those concerns color the words used to describe those needs. A developer is going to want to discuss something you designed because it is difficult using the framework he intends to use, which he chose based on requirements the stakeholders came up with. The project manager is going to be looking at how the product features work with the marketing, the budget, and the other products that might already exist and control to some degree this project's scope and look/feel. There's a lot to know, and you won't if you don't work with others. 

Collaborating is fun because we're humans.

Learning Your Limitations 

One of the most important things is to realize that you don't have all the answers. I tell my teams that I believe everyone is creative, and everyone can contribute to the creative process. The more ideas the merrier, and I can't count the number of times a developer, manager, or other designer came up with an idea I hadn't thought of but loved. If you want to grow, absorb like a sponge. The mark of a well seasoned designer is that he doesn't always have to be right. He'll argue a point, but he'll also latch onto great ideas and promote creative thought across a team. You'll also come to understand that you have many gaps in your knowledge, and you'll be able to create lists of gaps that you need to focus on moving forward.  

It's FUN! 

Collaborating is fun because we're humans. That means we're naturally social creatures, and at our best when we are interacting with other humans. Working by yourself can be deeply rewarding, and I recommend you do so on certain projects, but in general you'll go farther, faster, and have more fun if you do it with other like-minded people. Computer work is inherently isolating-there's no need to make it more so than necessary.