Related to #2 and #3: don't fall into the trap of believing that it's supposed to take a long time to do something important. Work expands to fill the time alotted. If you get it in your head that the Great Work you're trying to do will take you some number of years, it will, or it will take even longer, if you finish at all.
Commit to yourself now that you won't let work expand to fill the time alotted. Don't accept that from yourself, and don't accept that from others. (Within reason; everything can't get done overnight, but a "multi-year research project" often doesn't really need many person-years worth of effort, it just turns out that way because people let it.)