sessmgr.exe is a process belonging to Microsoft's remote assistance windows plugin. This allows an end user to call for assistance when a remote assistance network service is in place. This process shouldn't be terminated if the fore-mentioned service is in place on your local area network.
Non-system processes like sessmgr.exe originate from software you installed on your system. Since most applications store data in your system's registry, it is likely that over time your registry suffers fragmentation and accumulates invalid entries which can affect your PC's performance. It is recommended that you check your registry to identify slowdown issues