When struggling ..... as in just out right blundering. Play people you are better than them. Build up your belief system so when you do make good moves you do not doubt yourself. Use them as practice. I say do this for 2 weeks or a little more. Anything past that may bring you to their level. Then play whoever you want even if they are 500+ above your rank.
When you want to feel like improving play at your level. Wanna have fun play stronger players, plus they will expose any weakness in your game which also gives you something to study. Have to figure what they did worked on so go try it out on others. 
Im kinda of new to the game but i want to get better ovbiously so going straight to the point i often have issues with paying attention such as missing a piece by focusing to much on one half of the board i have begun reading books(bobby Fischer teaches chess and the complete book of chess strategy) so should i play people thats are better then me or at the same level to get better? If there is any more books i should look into please let me know and feel free to check out my games if you want to give me any further advise thank you