Be wary of the word 'Should'
In this situation, just pause.
'I should eat healthier'.
'I should not think this way'.
'I should join the gym and use it'.
'I should do/act better'.
Not to say these are necessarily bad thoughts.
It just depends on the situation, and what you want to say.
The problem is around the word 'should'. 'Should' is an instant trigger for guilt and I guarantee you that it will drag you down the road of negative thoughts and cause you to be frustrated.
you need to stop these thoughts starting with 'I should'
'Should' is a demand statement, so all it will do is cause anxiety.
I really hope this is of some help to you.