One of the number one statements I hear when customers are looking at clothes is, "I don't think that would look good on me." Which simultaneously breaks my heart and makes me determined to show them that they can pull it off.
First, some ground rules. You can wear whatever you want and never let anyone tell you that you can't wear something (including your own voice in your head). Remember that we are often our biggest critic and self love starts with what we say to ourselves about ourselves.
Secondly, know your body. Do you have long legs and a shorter torso? Do you have short legs and a long torso? Which part of your body do you love to show off the most?
Knowing your body's proportions, experiment with some different styles. For example since I am shorter (5'4) I tend to avoid a whole outfit of super baggy or oversized clothes because they make me look shorter than I am. I gravitate towards wearing super high waisted jeans to make my legs look longer since I know I have shorter legs. I also keep in mind that my torso is long, so bodysuits can fit funny or be uncomfortable (meaning I try them on to see if they work, instead of completely writing them off and saying I can never wear them). By knowing my body I am able to help make my legs look longer and keep myself comfortable.
Don't be afraid to get something tailored. If you find that pants tend to be on the long side, get them hemmed or on a budget get some iron on hem from the fabric store. If you love a dress, try to not write if off just because it doesn't fit perfectly, consider ways you could have it tailored for that custom perfect fit.
If you have long legs and a shorter torso, you might consider if you love to show off how long your legs are...go for it and wear those super high waisted jeans and try a French tuck for your top (tucking only the front in behind the button of your jeans and leaving the rest out). If you have a shorter torso maybe you make it look longer by leaving your shirt untucked to balance out those long legs.
If you are wearing baggy pants (wide leg especially), wear something more fitted on the top to balance it out. Or if you are wearing something oversized on top (maybe an oversized graphic tee) wear something fitted own the bottom (such bike shorts or skinny jeans).
Remember no one is noticing the things about your body that you are noticing. Focus on self love and remember that all bodies are good bodies. Your body keeps you going everyday and that in itself is a beautiful thing. And never tell yourself that you "can't wear something" because that is not true!