The concept of more/better is innately human. To “fix” it you first need to understand that everyone, everywhere regardless of circumstances feels that they are not doing certain things they “should” or could be doing. Even multimillionaire self employed people who jet set across the globe. Even the happily married couple who are madly in love and expecting their first beloved baby. Even monks who have almost mastered inner peace. Everyone. Sure some of us feel more fulfilled than others based on who we are, where we came from, and where we are going, but this general feeling of "is this it? should I do X differently?" is normal, especially in regards to careers. This means that wanting more/better, isn’t necessarily indicative of anything lacking in your life, but just a natural urge many of us feel even if we are doing awesome things. It can be a sign that you should make drastic changes, but many times if you are already in a good place, it is more indicative of the hedonic treadmill (we adapt to what we have, and then we want something different).
I try to fill this urge by setting goals...financial goals, travel goals, age based goals, daily goals, health goals. Some are very formal and specific, others not so much. But goal setting keeps me working toward something, keeps me motivated, and makes me feel great when I achieve them. The beauty of it is there are always more things to aspire to that do not necessarily involve massive life changes.