Magic doesn't happen when you successfully forced yourself into thinking positive. You might just add another stress: "What if it doesn't work next time?", "OMG, another negative thought, I need to fight it now.", "What if I just don't believe my positive affirmations? That proves I am not good enough, too weak, not trying hard enough."...etc.
It doesn't happen, when you fight against "negative thinking". It is not so helpful to pressure yourself into "having to get rid of" the anxious thoughts, "I should let go of" something.
Magic can happen when you can allow yourself to have "that thought" and it doesn't resonate with you in terms of stress or anxiety.
Magic happens, when you stop "working on it", fighting, trying too hard. A thought comes and goes, another thought appears, passes.
Just take a moment and play with that idea:
As you sit comfortably, you can close your eyes, allowing yourself to sink into the chair, becoming aware of your weight in the chair, the space you take and ll the space around,
and just be.
Notice a thought coming as it emerges.
Are you even able to notice the thought as it emerges? Or was it already there, when you became aware of it? Could you hold it or did it already pass?
That thought, was it an image, a little movie, a sound, words?
Notice when it is gone. Really try and catch that very moment.
What happens then? Is that thought you just had already replaced by a different one? Is there silence?
Just notice without judgement.
All those thoughts didn't tell you anything about "the truth", "the reality", did they?
As they come they go, like waves, as you internally switch, the thoughts switch.
Realising the chatter that goes on as chatter, not more, not less, can be really freeing and easing. Enjoy to contemplate that.