Clearing your thoughts before meditation

I'm pretty damn sure I'm not the only one out there that can clear your thoughts while trying to ground, or do meditation... I always end up thinking something while trying to clear my thoughts...

I have to stop to think... but how do you stop your thinking process... to not to think...

I know I wasn't like this before... dunno why it's like this now... I can't imagine anything or see/feel anything clearly. vividly I was able to during John's beginners class but was that because his place was clear of negative energy??? I try at home to see if I can see what I saw at John's place... and nothing... I have to stop trying and just relax but... it never works... I always end up thinking/feeling that something is near me and I have to be cautious....