Burning Bridges

I was asking myself if burning bridges or the other saying “burn the boats” was a good thing.
Apparently burn the bridges was born of a practice of the Romans when they would burn bridges to prevent a way of escape and supply for an enemy.  We know it as meaning “the inability to revert to an earlier state or position".  Although it probably refers to the Roman practice, it was not a common term until the 18th century.
Similarly burning boats was a strategy used by some when arriving in a foreign land to signify this was it.  There was no going back.  Win and make a go of it, or lose and probably lose your life.  This phrase was born around the same time but is less popular than burning bridges.
The question I was asking myself was, is the burning of bridges a good or bad thing?  My conclusion is either depending on the circumstances.
I know that for jobs I have left I have always endeavoured to leave on good terms with the people where I could.  I did not burn my bridges because I felt it was important my needing to perhaps return was seen as a good thing, and I would be wanted.   One time that is exactly what happened.
I have seen people burn bridges but with very different results.  One mortgaged their house to start franchises.  It was an all or nothing thing and worked out really well.  They have a number of franchises now and only work one day a week.  Others work for them.  That person spends their days readying the paper at the beach.  The other person burned their bridges and came totally unstuck.  They are back doing mundane things now.
 For me there is a time to burn bridges and a time not to do it.  I am a big believer in a plan B where I think appropriate.  I may or may not use it, but I know it is there.
It seems to me though there are sometimes where it is appropriate for me to burn bridges.  I have found it to be particularly so when making life decisions.  By burning bridges I am declaring to myself and others I am in this for the long haul.  That my decision was not made on a whim.  If it is, I reckon there is a good chance I will have opportunity to return to where I came from.  After all I have made provision for it.  It may not be right to do, but at the first sign of difficulty, or that things are not going according to my plan, I will use what is available.  And perhaps miss out on something better that is available through pushing through.
Whatever the case I reckon it is best to weigh options and make informed decisions.  Burning bridges or boats is a biggy in my mind.  Not something I will do on a whim.