You should follow the projects that allow you to either 1) grow yourself and your skills or 2) meet people you admire and can learn from

You can use the 'fear setting exercise'. Answer the following questions: 1) What is the worst thing that could happen if you chose to do it? 2) What steps could you take to repair the damage? 3) What are the outcomes or benefits of more probable scenarios? 4) What is the cost of inaction? and 5) What are you waiting for?

The rule of thumb I use is the 'full body yes'. You need to check if your head, gut and heart say 'yes'. If at least one says 'no', then you shouldn't go for it.