The most defeatist thing I hear is, ‘I’m going to give it a couple of years.’ You can’t set a clock for yourself. If you do, you are not a writer. You should want it so badly that you don’t have a choice. You have to commit for the long haul. There’s no shame in being a starving artist. Get a day job, but don’t get too good at it. It will take you away from your writing.
I agree with most of this, but I think it’s OK to get really good at your day job. First of all, you always have the option to stop doing your day job — it’s not like you will be magically forced into accepting it as your permanent career.
Second, the better you are at your day job, the more you will enjoy it, all things being equal.
Third, the better you are, the more money you will make, which really comes in handy if you want to start producing what you’re writing.
Fourth, if you are really good at it, you will have more career security — you can take off 3 months to write and then find another job in the same field because you’re really good at what you do.