Blueberry muffin was perhaps a little direct, but honestly, I have been thinking the same thing. And I think it about every poster who comes here with an issue that could be dealt with by talking to the person (or people) involved.
Now, some posters will ask, "how should I tell X person how I feel about Y issue?", and that is a valid question.
If a poster asks, "how should I deal with Y issue?", and doesn't even consider that they should talk to X, then that is usually indicative of a communication problem.
Speaking directly to the person involved, if that's a relationship you want to nurture, will always get the best results. Of course, you might have to look inside yourself, and figure out why something is bothering you first. Then express your concerns with honesty and tact.
Wife looks bad in her jeans.
Ask yourself: why does this bother me? Is it more important to me that she wears what I think looks good, or that she feels good about what she wears? etc,etc. You'll probably come to the conclusion that it's best to say nothing, unless your opinion has been directly asked for.
Wife cooks a bad meal
Ask yourself: why does this bother me? Is it something she will cook again? I don't want to eat a bad dinner. Best to say that I wasn't a fan of specific elements of the dish (rather than her cooking in general), and if she makes it again, could she change those things?
Wife can do more challenging workout
Ask yourself: why does this bother me? Do I worry that she's bored with the workout? Then I'll ask her.
Do I feel like I'm not the physically stronger one, and that bothers me because I like to feel like the 'man', and now I have a wife who is demonstrably fitter than me? Especially since I have recent health diagnoses that make me feel weaker than I used to be? Again, I should talk to my wife, since she's supposed to be my support in life. I should let her reassure me and bolster my confidence, because that's what spouses do for each other.
Honesty with yourself and your partner about your concerns and the motivations behind them is key. Seeing your partner as a code to be cracked generally leads to bigger issues down the line.