Once you have declared bankruptcy you must follow the process through to the end or you will remain un-discharged. Being un-discharged means that any interest you subsequently acquire in assets (house, cars, inheritances etc.) would belong to the Trustee. As well, if the Trustee is discharged, then your creditors can begin collection action against you again i.e. garnish your wages.
If you have filed a Proposal you can decide to stop your payments at any time if it is no longer something you can manage. If you stop your payments for more than 3 months worth of payments, then your Proposal is automatically over which means that your creditors can begin to collect against you again. There is some limited ability to start your Proposal over again, but it is not guaranteed that your creditors will agree to the process. As well, if you have filed a Proposal and defaulted on your payments, you cannot attempt to file a different or new Proposal for 6 months.