Can you post a game where this happens?
As far as I know ... you calculate as long as there are forcing moves left in the position in the line that you are proceeding in. Simply put, are there still checks/captures or threats left in the position ... if so, it is normal to continue to calculate them out.
How accurate you are with this + how well you hold these lines (moving pieces in your head) takes a lot of work and more experienced players can do this far more efficiently ... but doesn't mean you can't start somewhere.
It is easy to stop calculating prematurely, thinking the smoke has cleared but there's still something forcing (in-between moves, unstoppable threats etc.) that you didn't visualize, often leading to the blunders you speak of.
I find most of my losses are because i simply didnt calculate something long enough in my head, so does anyone have any pointers as to knowing when long calculations are nessary.