Pacing my friend, pacing is a key element of any games. Are there easy fights in my games? Of course there are! Deadly fights? Sure as he'll! But not everything is easy, and not everything is hard. The hard part is in playing monsters/foes in an optimal way, just like the players play their characters to the best of their abilities. For that, you need varied encounters that avoid mono type foes. Why send 12 hobgoblin warriors when 6 would do it and then add 2 hobgoblin cultists with bless spells and 1 hobgoblin apprentice with a few magic missiles or even sleep spells? This amount mote or less the same challenge but the varied type make it much more interesting and challenging. Use tactics, do not les the foes stand in their assigned area until the PC challenges them. Let their foes hunt them when the players go to rest. Put up traps and hazards that were not there their first time around. Make patrols more deadly as their foes learn from.thwor mistakes. Too often, I hear less experienced DM say, ok you go to sleep and you wake up the next morning... This is not often the case in my games...