re "Does anybody else have this problem? How do you deal with it?"

I'm a 41 y.o. management consultant for tech companies. Am I successful now? Because I published my second book last month, some think I am successful. But I feel like I am only getting "warmed up" and, at best, I am at 30-50% of my potential. Do I compare myself to others and feel regret? I do. For example, I look at what Eric Ries has accomplished. I admire him a lot, and I think he deserves all the success he has achieved, but ask myself why I didn't do more in my 30s. Another person I admire is Nir Eyal. Seeing what he's accomplished, I wonder why I didn't do more in my 20s and 30s! Actually, I got to interview Nir a few months ago, and discovered he's a normal human being, not a superhuman creature.

Here's some advice. (BTW, my training and expertise is in industrial-organizational psychology. It's not clinical psychology but the psychology of: individual performance, team performance, motivation, engagement, etc.)

Plenty of successful people struggle with self-doubt, self-criticism, and anxiety. For example, I struggled with depression in my 20s. Whatever your pain, it is your cross to bear. Learn to manage your condition, and you will become a stronger person, and better able to help others who struggle like you did.

Learn to deal with setbacks and disappointments without freaking out. Learn to meet adversity and hardships with equanimity -- with an even mind. Keep driving towards your goal but be ready to change your plans as you go. When I was 34, my dad died quite suddenly. It was terrible. But from that hardship, I decided to take action toward my goal of becoming a management consultant. I started down that new path. Three years later, I got my Masters degree in industrial-organizational psychology, and was excited about starting my new career. Weeks after my graduation, our youngest child was diagnosed with a chronic condition for which there is no cure. I had to change my plans around for four years mostly because I needed to learn to care for my daughter. She's doing well today because we put her health and well-being first.

Self-compassion is important. You can be compassionate with yourself while continuing to work and get progress made each week. You may want a coach or a professional counselor to help you sort through this.

Some will tell you to "have no regrets at all" because they want to help -- ie. get you to stop worrying so much. Actually research tells us that some degree of regret can serve a useful purpose. The problem is overwhelming regret and shame. Again, the solution and antidote to all of this is self-acceptance and self-compassion.

If you want to be successful, the research points to success being determined by how many people you help to become successful, and how much talent you multiply in others in your community of peers and your network. Look at ways to keep improving your own skills but help others get more skilled and successful too. Read the book "Give and Take" by Adam Grant.

Last but not least, you can't stop your mind from comparing your achievements to others. But you can learn to observe your mind and your thinking, without "buying into it" or being a slave to that train of thought. Take a course in mindfulness meditation. You have many good years ahead of you.