I don't know if it's a trend or timing or what, but I've recently noticed several posts on boards regarding self-inflicted guilt. It concerns me when people do this to themselves. I'm not saying that you shouldn't have a conscience. However, to devote a lot of one's energy feeling guilty seems like such a waste, especially when the object of your guilt isn't something that's your problem or it's relatively minor. Save the guilt--you're holding yourself back with misplaced feelings of guilt or shame.
For example, you've been holding on to a special occasion dress for years and you know you'll never wear it again, nor will your children. You don't even think it's that well made. Yet there is guilt over disposing of it. Why? Pass it on--to someone else it could be perfect for their special event. It would be a blessing for them to find it at the thrift shop.
Or you sell things on eBay. IMO, it's not your problem if the price is bid up beyond the value you would place on it. Now, an important caveat is that you presented the item clearly and truthfully with no deception (if so, shame on you, you should feel guilty). But otherwise, no. You are not responsible for the bidder's decision making process. Perhaps they have a special reason that they have to have your item, or maybe they have more money than sense. These are their issues, not yours. Don't presume you know better than they do.
Then there's the case of having a degree and not "using" it. Personally, I won't sew for other people. But if that's what you want to do right now and are fortunate enough to be able to afford to build a business, then go for it. Perhaps a break from your career is what you need. Maybe you'll go back to it someday, maybe not. It's a business decision; don't feel guilty. Channel those emotions into a plan for the sewing business, so you can make it work for you and your lifestyle. And be sure to charge enough--don't let people "guilt" you into giving your skills away.
Or guilt at being able to sew but taking items to a tailor to be altered. Look, if you were inclined to do it yourself, that blazer would have been altered already. Instead, it's been sitting in the closet (yet another occasion for self-inflicted guilt). Why not have someone fix it up for you? There's no reason to feel bad about it. You don't have to sew everything you wear, nor do you need to do all your own alterations. I outsource most of my alterations because it's just not how I want to spend my limited sewing time. Also, I've actually learned a lot by watching my alterationist pin up my garments and seeing how she made the adjustments.
Build yourself up instead of tearing yourself down. Let go of misplaced guilt. I say this not as a putdown, but because I think it's important to feel good about yourself and your decisions. Guilt directed to you from others is another topic, but first things first--be kind to yourself.