How to control sleep during simran?

1. Why sleep disturbs us in simran. For example we are alert for normal one hour, but why it's not possible to be alert in simran's one hour after first some minutes?
2. How we can control this sleep? Some say we can stand up, but it seems not better option.
3. Any other suggestion or guidance regarding this issue is most welcome.

in the absence of sabad surt mel, verag, waheguru nu milan da chaoo....then neend come ....

only ardass , gurmat vidhi to jaap namm , cold water bath , is best to avoid neend

ਲਗੀ ਵਾਲੇ ਤਾ ਕਦੇ ਨੀ ਸੋਂਦੇ , ਤੇਰੀ ਕਿਵੇ ਅਖ ਲਾਗ ਗਈ

Thanks for giving this inspirational line. But here in indian summer staying outside as a paying guest, pls give explanatory answer to this sleep just after crossin some minutes of careful naam abhiyas.

It will take getting used to. You can try breaking up the sitting into 2 half hours or maybe three 20 minutes? You can also alternate between sitting and standing. Inspired by Guru Amardass ji I try standing sometimes. Sometimes I try jaap while standing. Sometimes when I am outside, like in a field or a yard or near some wall, I face the wall and do some simran. I like it. Of course it does not match the complete privacy of a room but still.