I do think it depends on what each model's definition of success is. For me, I've reached way over my goal so I consider myself to have "made it". I've been consistently in the top 100 since I started on MFC unless I decide to take a lot of time off throughout the month. Being non-nude, I thought I'd be ranked in the several thousands (at least) and almost completely lost in the abyss on MFC. I couldn't have been more wrong. I realize even being nude on MFC, it usually takes at least a few months to get this kind of placement so I feel amazingly grateful and humbled by my experiences and success.
It's a bit tough to explain my ups. If I had to put it into words, there are of course amazing moments like high tips and funny jokes but it's more so about building a community of friends for me. There seem to be quite a few guys on MFC that are looking for a place to hang out and need a friend / group of friends. I needed the exact same thing so it was very easy for me to relate to this kind of loneliness genuinely and just all hang out and be friends and have fun together. In this way, MFC is more than just a job for me, it is also comprised of my friends and much of my social life. Building this has been and continues to be my up. Off cam, we play video games together and it's just an all around great experience.
I'd say many of my downs have to do two things. The first is when I meet someone and they seem super cool but, for whatever reason, have to leave or can't come as frequently as before. This can be due to getting a girlfriend, a change in work schedule, or even deciding I'm not the right model for them or what have you but it always sucks when this happens. The second down for me is when I set really high goals that aren't easily achievable. On these months I have sometimes stayed on 10-12 hours a day consistently. After a while, I realize I need to re-charge to be able to be at my best for everyone on cam so I try to be careful not to do too much.
All in all, I really love and am amazed by everything on MFC. It has certainly changed my life. As others have mentioned, there is always room to grow and it can keep you on your toes. For me, I strive for a balance between ambition with wanting to move even further along in the ranks but also to remember to recognize and be grateful for what I already have and achieved.