As a consultant and writer, I need to juggle a lot of different deadlines and demands. I've found that the best app for me is Asana. It's customizable, so I can adapt it to every project while maintaining a cohesive calendar with all of my deadlines.
That said, I also pair Asana with an old-fashioned notebook and pen. Instead of writing to-do lists, I write have-done lists. At the end of the day, I benefit from a clear picture of what I've accomplished that day — it allows me to step away from my work with a clear mind, knowing that I've tackled a fair number of projects.
If you need help managing your projects, feel free to reach out for my input. I've written about productivity for Fast Company, Inc. and Entrepreneur — I would love to share more thoughts with you.