There's definitely something ingrained in a man's psychology that leads us to associating our entire sexual identity with just our penises. I think a lot of that goes to how many men develop sexually - I think it's much more common for a man to primarily just want his genitals rubbed, and he's with someone who just concentrates on the rest of his body but ignores that, it feels really frustrating. Very few women (in my experience, 0) just think about their clit + vagina when they think about sex. Even when sex is purely physical, it's more of a whole body thing. Not saying some/most men don't like to have other places touched, just that it's weighted more strongly for women.
As such, whenever we feel depressed/inadequate, because we're making the mistake of tying so much of our identity to our dicks, they can seem small.
I find a good reality check helps in order to stay objective. Knowing the stats is good, but there's something unfulfilling about just knowing how many standard deviations you are from the median. One that I find pretty useful is to check the rare scene in big-dick porn where you can actually get a frame of reference on them (even if not a very good one.)
e.g. here:
http://x-images4.bangbros.com/monstersofcock/shoots/mc541/members/450x340.jpg
if you actually read the tape measure, this guy is maybe 7.5" long, and that girl is
very small
or here:
http://x-images4.bangbros.com/monstersofcock/shoots/mc854/members/450x340.jpg
if you notice how the tape starts at 2 and is cut off, this guy is another fellow <8"
yet another:
http://x-images4.bangbros.com/monstersofcock/shoots/mc838/members/450x340.jpg
so her tape is well-below the dick and from the side which can add over a whole inch, so definitely another around 7"
Here she compares to a beer bottle:
http://x-images4.bangbros.com/monstersofcock/shoots/mc8469/bangbros/big3.jpg
if I hold a beer bottle up to myself in that position, if anything I go a little longer than he does. You might think he's just not at 100% there, but it's not like monstersofcock.com is known for underselling its dicks. His girth's also pretty close to mine.
From the same photoshoot with a ruler:
http://x-images4.bangbros.com/monstersofcock/shoots/mc8469/bangbros/big4.jpg
For those of you who are unfamiliar, the centimeter side of those rulers always goes up to 30cm, yet you can clearly see it's only at about 20cm when it's near his base. Also take in to account that he's holding his dick way closer to the camera, and again, yep "only" about 7.5" long, yet it's being sold as a footlong dick in porn/internet inches
So to see that not just guys in porn, but guys in big-dick porn (ie guys who have big dicks compared to other guys with big dicks) are in the same area as me makes any worry about it seem absolutely ridiculous. I'm sure some guys might _look_ bigger, and a few guys are significantly bigger, but to qualify for big dick porn and be worried about your size at all is downright paranoid.
For those average/smaller than average guys out there, I hope you can look at this and realise that your concept of a 'huge' dick is probably way off from the reality.