I've recently hit the 5-star quests, and I'm kinda getting bored. I've been using the Velocidrome Armor set for what feels like forever, and I've had an Accelerated Hammer for equally long. It looks like I can finally upgrade my weapon soon (I just killed the Seltas Queen), but I'm not sure I even care to. It'll look the same, won't it?
Furthermore, the game's side systems are starting to overwhelm me: cat quests, Sunsung Isle expansion, ingredients, etc. None of it is jumping out at me as being especially important, but I'm sure I'm missing something.
Can anyone help me get the fire back? I really want to go the distance with this game.
edit: I've been playing for nearly 40 hours.
Based on your comments I'm assuming this is your first Monster Hunter? It is mine at least. And that you haven't already been playing online?
I played up through 9-star offline (caravan) before I started experimenting with the online (guild) missions. I'm personally happy that I did it that way. I was able to learn the flow of combat and the detail of the game's systems before playing with other people. But now that I have dipped my toes into online, it's hard for me to not consider that the main mode going forward.
I generally prefer to play games offline, but I have enjoyed playing online Monster Hunter with randoms quite a bit. If you haven't tried it yet, my advice would be to just pick a random room and just join in on whatever they are doing. If you are totally new to online, make sure you choose a room of the apropriate hunter rank (for a beginer that would be HR1-3), that it is listed as "in guild hall" and not "on mission" (this just means that they are about to start a mission instead of on a mission), and that it has 2-3 people in the room already. And then just play whatever missions the other people are doing (once they choose a mission, you have to sign up for it on the board next to the exit door, and then go to the exit door).
Once you do that a bit, you will get a sense for the dynamics of those play sessions and how/when you should ask to select your own missions. This relates to "key" quests versus "urgent" quests, but I wouldn't even worry about that to start with. For me, playing online is more about -playing- than about strict advancement. You are going to end up repeating missions, but that's ok since missions go super fast online and there is always a use for extra materials.
Regarding needing motivation to push forward, I have personally always been motivated by getting better gear. Having watched a lot of tutorials online and having been exposed to advanced players, it has always been painfully clear that there is better gear waiting right beyond the corner. I have always been two steps ahead of myself regarding what monsters I am waiting to fight so I can craft their bows and/or armor. Another benefit of playing online is that you will be exposed to everyone else's equipment, which can help to point you in the right direction.
Other general advice:
The various game systems come to matter more as you advance further into the game. And none of them are individually as complicated as they might seem. I wouldn't worry about any of them until you feel you need to or until you run into a difficulty wall.
Combining items will become useful if you come to use items on quests. You will want to build up an ecconomy in the game to keep yourself stocked. But, again, ignore that for now if that isn't your play style. Though I would assume that you would want to be crafting mega potions at the very least.
The cat stuff can be useful if you want to put time into it, but you can also larely ignore it. Having spent a lot of time offline, it was very helpful for me to have built up a set of palicoes to auto-heal me (healing is a pain for archers). If you're interested in this, you can google "first-stringers"/palicoes for info.
Armor skills didn't really matter for me until high rank (caravan 7 and up). I would just pay attention to what skills your armor has so you can start to learn about the concept in general. Like these other systems, you don't really need to worry about theme early on, and you will learn about them organically as you play.
One last comment: don't be afraid to experiment with other weapons even this far into the game. The Hammer might just not be right for you.