I have never tried to sell my collection just because I really doubt it is worth anything.
I hear that! There have been a few times I thought, and said, the same thing.
Plus I would be afraid if I was offered a decent amount that I would accept it.
Depends on what we think "decent" is, $$$-wise. If you're like me, you know you wouldn't get anything near what the actual value is...maybe 10 to 20% (or less). That said, it's a tough call sometimes, especially when $$$ is tight, or non-existent, and you have a need this or that.
Eh, I'm inclined to keep mine, for that reason alone, but another good reason to hold on to 'em is handing it off to someone in the family later in life. My kid isn't into cards, but maybe he'll have kids of his own someday, and he can give 'em to them, if I'm not around to do it myself. I basically told them to do just that, that if something happens to me, don't bother trying to sell 'em, unless they really really really need the $$$...and I warned them they likely were not going to be offered much $$$, in any case.
One final reason to keep them is the historical value, family-wise. When I post images of my cards here, those images are highly likely going to be easy to find, even after decades. Kids, grand-kids, nieces, nephews, etc. will very likely be able to find images of the card I once had. Better yet, if they have the card themselves, they can look-it-up and in that way have a connection with me, even hundreds of years from now.
I really really really like that thought.