I was at my music class today, which I used to attend on a regular basis and still love, but I have now cut-back on attendance because I actually want to finish my current book and need more hours to myself to make it happen.

Yeah right!  You can sense when you mention to your colleagues "I want more time to write" you actually are not being taken seriously.  The reason is not your friend or friends being nasty.   It is simply because "almost everyone wants to write"!  When a friend wants to make cakes and sell them, or work in a bank, or in a department store, we all support our friend and wish them well.  It is, however, difficult for them to visualise, no matter how fond they may be of you as a person, that you are actually really going to write an authentic story which others would actually want to buy.  You, however, know that you can - and will.

That involves commitment, discipline and a real belief in oneself.  You want to write because that is what you love.