No, you don't have to keep your home on the market if you don't want to. No one can "force" you to sell your home. Even when a home is facing foreclosure it is still up to the homeowner if or when they want to list their home for sale. The option to allow the home to go back to the bank exists and if the owner chooses to allow that to happen they can.
Regarding your situation, if you truly don't wish to continue to sell your home you can remove it from the market by asking your agent for a Cancellation of Listing which you sign and they sign to remove the home from sale.
Be aware however that removing your home from sale, taking the sign down and taking it off the MLS do not absolve you of having to pay the agent with the listing currently a commission should you decide before the expiration date of the contract you originally signed (or any extensions you may have signed) to relist and sell your home, or if you sell your home to someone that they helped you find.
There are some rules about what the agent would need to do in order to be in the best position to collect their commission, but the possibility that you would need to pay them and everyone else involved in the transaction does indeed exist.
Read your listing contracts carefully as most your questions can be answered by a perusal of these documents. Generally, unless you specifically changed it when you signed the document, most listings are six months minimum and one year is usual.
I do agree that if you are choosing to remove your home from sale, it would be courteous to say the least (and you may be contractually obligated depending upon what you agreed to at the time you entered into the agreement) to offer to reimburse the agent for any out of pocket expenses they incurred on your homes behalf. I would ask them for an accounting of any expenses (advertising, virtual tour costs, sign erection, etc.). Times are tough for everyone and, to appropriately and aggressively market a home is not free or for that matter cheap.
One other thing I would suggest, especially if you are removing your home from sale for any reason other than the fact that you have just decided now is not the time to sell it, is to talk to your agent and/or their broker regarding your decision and why you have made it to see if any issues you may have could be resolved.
Again, no one can force you to sell your home if you no longer wish to. I tell my clients at the start of our relationship, that if they are unhappy with my performance or just plain change their mind about selling all they need to do is tell me and we will cancel the listing, no harm, no foul. Of course this works both ways, I can decide that I don't wish to continue to represent them as well so it keeps us on even footing.
Good luck with your situation and if you have any other questions please do not hesitate to ask.
Take care and have a wonderful day!
Tisza Major-Posner, Realtor, IVPG Realty (909) 837-8922 or (213) 392-4084