While you may be able to control your outward appearances you may not be able to control your inner feelings and this is what is causing your tears to build. At some point I would guess your tears do start to fall and when they stop the redness in your eyes clear.
In short this is an emotional response. Controlling ones emotions, especially at your age is something very hard to do. Should you find yourself crying for no apparent reason do not be overly concerned as this is a natural reaction to puberty for some girls. I would suggest talking to your mother about this and consider seeing your doctor or your pediatrician as there is some medications that can help you deal better with the effects of puberty. [ adviceman49's advice column | Ask adviceman49 A Question ]
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