In a world that is as competitive as the one that we live in now, there is every chance that the work you put up for inspection or approval will be met with criticism. It could come from peers, seniors, and colleagues who have worked with you in the past or have known you for a long time.
While some critics could be justified in their observations and following them could really bring in a lot of improvement in your product, there will be a few who would pass judgement purely based on emotional reasons like personal hatred, jealousy, one-upmanship, etc.
Remember that you cannot satisfy everybody. It is just not possible. There will always be scope for improvement, but you need to think practically as to what is the set of parameters that you need to keep the quality of the output under.
A self-confident man would be really quick in finding the difference between both. He would appreciate and acknowledge the errors and areas of improvement as suggested by the constructive critics, while ignoring the criticisms of the latter.
The real reason people face an issue dealing with criticism is that while doing their work, there are chances that you get attached to your output and an emotional bond forms. Imagine a chef who lovingly and caringly prepares a soup. Now when faced with a set of judges, who pick and analyze every single ingredient and herb, a person is bound to feel that the judges are slightly unemotional in their assessment. It is this divide that causes the initial tension in every feedback session. A person should remember that emotions and personal dislikes have no place in criticism.
Now how to know whether a criticism is just and constructive? The first thing we should check is whether the criticisms are practical and flexible or are they draconian. They should allow exceptional cases and individual capability. In general, be wary of criticisms that use words like − "never, completely, all the time, totally".
You should also check for yourself and see if the value they are expecting out of you is achievable or not. If no, then they are setting unrealistically high expectations on you, and it will only lead to bad news if you start entertaining those thoughts.
In a professional scenario where many talented and creative-minded people work, there is always the chance that someone suggests some modification or change or enhancement to your output. If the objective of that feedback was to produce better performance, then it is justified. However, if the feedback is just to point out vague errors using personal dislike of a thing, then those criticisms are valueless.