Here two objects are used.Account and Schedule__c.
The main block's code is called by before trigger on account.
Trigger is on Account object.
It is not allowing me to update the Schedule__c object .

Please let me know why this error is encountered.


Error : 
Error:Apex trigger Account caused an unexpected exception, contact your administrator: Account: execution of BeforeUpdate caused by: System.DmlException: Update failed. First exception on row 0 with id a0JM0000007bp55MAA; first error: CANNOT_INSERT_UPDATE_ACTIVATE_ENTITY, Schedule: execution of AfterUpdate caused by: System.DmlException: Update failed. First exception on row 0 with id a05M000000ACmimIAD; first error: SELF_REFERENCE_FROM_TRIGGER, Object (id = 001M000000uSEuz) is currently in trigger Account, therefore it cannot recursively update itself: [] Class.ScheduleTrigger.updateCallsForSchedule: line 63, column 1 Trigger.Schedule: line 11, column 1: []: Class.AccountTrigger.NextCallCycleCheck: line 248, column 1

Main Block :
system.debug('Inside 6week block ');
                 a.REX_Call__c=false;
                 boolean acctNextCycle = a.Next_Cycle_Call__c;
                 List<Schedule__c> wk6Schedules = new list<Schedule__c>();

                 if(a.Priority_Cycle_Frequency__c == 'K: 6 Week Cycles: Weeks 1-2' || a.Priority_Cycle_Frequency__c == 'L: 6 Week Cycles: Weeks 3-4' || a.Priority_Cycle_Frequency__c == 'M: 6 Week Cycles: Weeks 5-6'){
                        system.debug('Inside 6week if block ');
                     for(Schedule__c schedule : [SELECT Id,Store__c,Week__c FROM Schedule__c WHERE Active__c = 'Y' AND Status__c = 'Active' AND Route__r.Status__c = 'Active' AND Store__r.Active__c = 'Y'  AND Store__c =: a.Id]){
                           system.debug('Inside schedule for loop ');
                        if (schedule.Week__c == 1 || schedule.Week__c == 2){
                               system.debug('Inside if block of week 1 and 2 ');
                            if (!acctNextCycle){
                                   system.debug('Inside nextcall true ');
                                reverseAcctNextCycleCall(a);
                            }else{
                                system.debug('Inside nextcall false ');
                                wk6Schedules.add(update6wkSchedule(schedule));
                            }
                        }else if (schedule.Week__c == 3 || schedule.Week__c == 4){
                            system.debug('Inside if block of week 3 and 4 ');
                            reverseAcctNextCycleCall(a);
                            wk6Schedules.add(update6wkSchedule(schedule));
                        }    
                     }
                     System.debug('all schedules to update are ...'+ wk6schedules);   
                     if (wk6Schedules.size() > 0) {
                         database.update(wk6Schedules);
                     }

Functions used in main block :
public static Account reverseAcctNextCycleCall(Account account){
         system.debug('Inside reverseAcctNextCycleCall ');
      Account schedAcct = new Account();
      schedAcct = account;
      if (schedAcct.Next_Cycle_Call__c){
        schedAcct.Next_Cycle_Call__c = false;
      }else{
        schedAcct.Next_Cycle_Call__c = true;
      }
        system.debug('New next cycle call :'+schedAcct.Next_Cycle_Call__c);
        system.debug('Exiting reverseAcctNextCycleCall');
      
      return schedAcct;
    }
    
    public static Schedule__c update6wkSchedule(Schedule__c sched){
    // if wk=1or2, +2 , if wk=3or4, -2
    system.debug('inside update6wkSchedule');
    Schedule__c schedule = sched;
    Decimal existingWk = schedule.Week__c;
    system.debug('Existing week : '+existingWk);
    Decimal newWk = 0;
    if (existingWk == 1 || existingWk == 2){
         newWk = existingWk + 2;
    }else if (existingWk == 3 || existingWk == 4){
         newWk = existingWk - 2;
    }else{
         return schedule;
    }
    schedule.Week__c = newWk;
        system.debug('New week : '+newWk+'schedule.Week__c : '+schedule.Week__c);
    return schedule;
  }