the poet says,"i took one less travelled by ,and that has made all the difference." What is the 'difference'thatvthe poet mentions?

'The difference' to me seems that the poet chose to be a poet. He doesn't seem to be happy with his choice. He regrets to have taken up the second road. But, it is after he has lived his life for some years. At this stage, he looks up into his past. Seeing that, he says that "this (his choice) has made all the difference". It shows his hesitation and sighing. But, life is such. We can't derive hundred percent contentment.