I cook for 4, but regularly make large batches and freeze the extra portions - so 5 or 6 pots of Chilli, or Bolognese, or 2/3 lasagne, fish pie, cottage pie etc.
If I was cooking for one, I would do exactly the same, but freeze in smaller portions - buy appropriately sized tubs/cookwear. For lasagne I would aim for a 2-portion size and spread over two days.
I do also make single-serving 'ready meals' of chinese curry with egg fried rice, or red lentil dhal - it's only me who likes those, and it's handy to have in the freezer for when I just need to feed me.