What has been the best productivity tool you ever used? And why?

Without a doubt Notion. It's free and has many features, with very few differences from the pro version. Templates you can copy from their website in the template section or a bit more creative templates you can find online (usually interest or redit). Youtube tutorials on optimizing Notion for everyone and every single purpose you can ever imagine. Work, faculty studies, writing content or a book, going to the gym, groceries, keeping a book or series log, the list is endless. I use it to organize day-to-day life, faculty, work, and content writing for work. It can be overwhelming at first since it's a blank canvas with many possibilities, so I recommend taking a template and modifying it to your liking.

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One of the best software solutions I've tried is GanttPRO (https://ganttpro.com/) Gantt chart task manager. This professional tool serves as the best helper in planning work, tracking tasks, setting deadlines, and collaborating with product stakeholders. It'll lead your projects to success and increase productivity for sure.