How can I make myself think my penis is bigger while masturbating

When you are masturbating the most important thing is your own personal pleasure. If you are lucky enough to have privacy you can really take your time and enjoy yourself. Use long, slow strokes. Using some type of lubrication can really enhance the experience by allowing you to glide over the entire shaft. I definitely don't get as hard or as big as I did when I was younger but I sure still enjoy my 'personal time' ;-)

For me, it depends on how turned on I am. If I'm extra turned on and enjoying myself, it definitely appears bigger. Maybe because it's extra stiff that day or something. But it's not every day. I also know that it's appeared bigger since I started losing weight. Not sure if that's any help to you but it's something at least. But I agree with the other person, just take time and enjoy yourself.