Are there really that many differences between managing small and big projects. When making the leap from small projects to big ones, it's important to reflect on things that worked and didn't work on smaller projects.
A Little Preparation Goes a Long Way
Small projects are usually easy to handle and summarize. It's pretty clear how to get from point A to point B when the distance you must travel isn't far, and that's pretty much the case for any small project. Yet, because a project is typically part of something larger than itself, you probably have some idea on what it means to take on the really big projects before they come your way.
When preparing to take on a big project, reflect on the past smaller projects that you've had. There are usually clear memories in a project manager's head of the times when things went very wrong or very right on a project; those are the unforgettable times in one's career. As such, it can help map the way for how you work on future projects. Accentuate what went right on the smaller projects for your road map on the bigger one. If you found delegating helpful, be sure to ask for a few extra hands that can work for you on it. If you found that conceptualizing was a big part of your success, do that. Whatever works for your personal small project success is likely to work on a larger scale as well. By comparing the experience on multiple projects, you can get an idea of what's working overall.
Time Management
A bigger project is going to mean doing everything on an increased scale. For instance, you will spend considerably more time on a big project. You'll need a bigger budget for expenses. You'll need more hands on board. You'll need a longer time for project completion, a much later deadline than would be given for a smaller project. Luckily, you usually have all of these. What's important is that you don't see that far-away deadline as an excuse for procrastination when smaller projects of less importance--yet with shorter deadlines--appear.
Give more hours out of your day to completing bigger projects than you would smaller ones because they require it. While this isn't true on all days, it's true on the majority of days. Your career is usually going to be more advanced or held back based upon a larger project than one of less importance to the company.
Things to Remember
If you find the idea of a bigger project intimidating, remember that bigger projects can easily be divided into smaller parts. Look at a big project as several small ones in succession if that helps getting through it easier. Tackle one aspect of it at a time. The small works will add up to your one big project. Along the way, it's important to remember to delegate tasks as needed.
Before you take on a big project, make sure to ask what the most important aspect of it is to the company. As you work through all the parts of the project, keep the priority constantly in your mind. That will likely lead to ultimate project success.