you need to monitor this values to make your server stable and safe   :  

-   CPU / RAM spikes
-   Disk usage 
-   Disk nearing full capacity 
-   Account exceeding limits  
-   Abnormal processes               
-   Alerts 
 

you should follow this steps to make this :

1- login to your WHM panel 
2- from right upper side choose Alert sign 


                                            



3 - monitor your Network - Cpu - Memory - Disk - Alerts


                                           




4 - if you noticed any thing you need to fix it to make your server stable and safe