If you miss a lot of putts, write down what you keep doing wrong. Later, your list might come down to this something like this:
'My downhill putts I hit too soft'
'I under estimate the break on large slopes'
'My putts from right to left are always short.'
'My uphill putts from left to right go long over the top'
etc.
So you refine your technique for each putt you miss. But if you don't make note of your shots, you can't refine the method.
If I always like "Too hard, over the top", "Too hard, over the top"
I'll change it to softer and maybe more inside till it drops.
Be confident. It seems to help me. But it only works if you're using the steps above!!