Once you start sending more than you want to spend just in case, you'll end up betting it all with no control over the bankroll, so it's much better to have limits established before you even start to gamble.
I don’t know about others but in the case of redepositing after I’ve used all my balance I’m able to control that one - most times I don’t even feel the need to go on with gambling, the thrills and vibes and I had initially dies off as soon as my first deposit gets exhausted. The only thing I know I still struggle to resist is the urge to not continue gambling when I still have a balance in my account or when I win and refused to make withdrawal - there’s always a high chance that I will go back to my account and use everything again till it gets to zero or if I’m lucky I’ll win more.