As you know, a great question invites effective self-coaching. Implicit in this question is the difference between perception and reality. Unchecked, this gap can turn a sound putting stroke into a mess of compensations and loss of confidence.
Am I aimed where I think I'm aimed?
Unsurprisingly, there is a high correlation between aiming your putter consistently well, and success. So it's worth forming a habit around protecting that ability. There are two applications for this habit. Firstly within your putting routine and secondly in your practice.
Pre-shot routine
Basically, the key is not to assume that the first time you put the putter face down, you've aimed it correctly. I see so many golfers who place the club behind the ball followed by no checking or corrections. We are not robots, so the chances of placing it within a degree* of your intended start line with no checking, is extremely slim. * You need 1 deg accuracy on start line, to hole inside of 10 feet.
Asking "Am I aimed where I think I'm aimed?" at this point in your routine, invites at least one or two confirming looks between the putter head and your intended start line, and the opportunity to make a helpful correction if necessary.
Practice
If you play golf, say, weekly, you need to ask this question at least once a week in practice. The difference between the on-course example above, is here you get extra feedback.
Whether you use a laser line, a second pair of eyes, or hold the putter in place on the ground as you move behind to get a better view...you must seek additional feedback. Note, putting on a putting mat with a pre-printed line isn't testing your ability to aim, so remove that from the equation before you ask yourself this question.
Summary
If you make this a habit, challenging and confirming your aim, you'll be less likely to be horrified at the result. As with all the habits I highlight, their simplicity belies their influence.