I handle it by not having more available credit than I need. I refuse the regular offers by my current CC proviers for limit increases because I have no intention of ever using credit cards for those levels of debt.
If its going to cause you problems with a loan, then cancel some of the high limit cards, or ask the provider about reducing the limits. They will be reluctant to reduce your limits since they want to lock you in to use them for credit, which is why they give such large credit limits in the first place.
Citibank tried to increase my Redicredit account credit limit by $10,000 last week. That is just rediculous since in the few years I have had the account I have never been more than about $500 in credit and that was only for less than a day. I use it as a free cheque account and in the past for overseas ATM withdrawals and transfer the fund into the account the same or following day. So what possible valu is there for my available credit limit to be increased to well over $30,000? None whatsoever. But there is every incentive for Citibank to get me to do it. I very nearly called them and said "thanks for prompting me about the value of my credit limit. Instead of increasing it by $10,000, please reduce it by that same amount. Oh and each time you ask me to increase it, I will call back and ask for a similar decrease until I am happy that the limit reflects the quality of the service".