I believe that statement. Whenever you compare two things, one of them will surely suffer.
If you compare what you have in relation to what someone else may have, you may begin to feel as though you don't have "enough" because they have more than you. The nice house, the nice car, the fancy clothes, the cleaning service, vacations, the weekly massage appointments or manicures are all things someone else may be able to do without hesitation but you have to budget and plan for two months to get a manicure wedged in let alone an eyebrow wax or a good haircut at a reputable salon. You may begin to feel slighted by life, by fate, and so begins the unhappiness that results from comparing what you have to what someone else has.
We don't often recognize and appreciate what we do have because we are so busy comparing it to what others have. "When you stop comparing what is right here and now with what you wish were, you can begin to enjoy what is." (~ Cheri Huber) I've heard reports of people who routinely use social media being more prone to depression because they consistently compare themselves to the personas that others put out there, to their own detriment. If you simply can't control comparing yourself or your lot in life to someone else's, at least let that comparison be one to inspire you as opposed to tearing you down and making you feel bad about yourself. Let it inspire you to make positive change in your life or use it to focus on something that is already positive about your life. When you find yourself tempted to compare your life with another's, stop yourself. Count your blessings. Name them, specifically. Change your thought pattern to one of thankfulness instead of envy or despair. Newsflash: It's OK to not be perfect. It really is.
In my own personal experience and in my current situation, I have a husband who has to live with a ghost, so to speak. I believe there are several who consistently compare him to my late husband only to attempt to illustrate that he's not as good as my late husband. I could be totally wrong about that, but I believe it has happened and probably still happens. When you have someone who has passed away tragically, all their good qualities are the only thing people want to remember. And when you have someone who steps into that person's "place," they will inevitably be compared and usually will suffer because of it. There are times when my husband fights an uphill battle to be recognized for his own good qualities, to have his true intentions and feelings not questioned but seen clearly, and not to be liked or disliked because of how he compares to my first husband. In a divorce situation, most people consider the fact that your new spouse is nothing like your old spouse as a good thing, but in my situation, that doesn't seem to always be the case. The negative feelings that result in him because of this comparison really tick me off because he's such a good person all on his own and deserves to be judged or appreciated for who he is and not who someone else was or is perceived to have been.
Which just leads me to assumptions. Don't assume someone has it better than you just because they have nice stuff. They could be swimming in debt while you live debt-free. Don't assume someone has it worse than you just because they drive a crappy car. They could have mucho bucks saved up and are just disciplined enough to not waste it on something they don't need yet. Do much less worrying about what other people have or don't have and start paying more attention to yourself and what kind of life you live. Focus on your own individual strengths and not your weaknesses. If you can't identify and focus on your own strengths, then what is it about yourself you are proud of? What do you believe your true value is if you always base that value on what someone else has?
"To love is to stop comparing." ~ Bernard Grasset