1) You're not alone
One thing is for certain, you are most definitely not alone. In fact, one third of the population will also be suffering with their mental health. When I was depressed it always helped me to think that I wasn't alone, and that I wasn't stupid to be feeling the way I was feeling, even though there wasn't much wrong with my life. There are always people out there that understand what you are going through, and people that want to help you feel better.
2) It will get better
I know it's easy for me to say now, but it will get better. It has to, because you can't continue to suffer for the rest of your life. Mental health is fluctuating, which means that you will have happier times and you will have sadder times. But the most exciting thing is that your happiest day has probably not happened yet - get the help that you need, push through recovery and you'll find it waiting for you.
3) Recovery is lifelong
The truth is, your mental illness is probably never going to go away completely. I feel like I have recovered from my depression, but I still have occasional days when I struggle and go back into the spiraling thoughts and irrational feelings. But that's okay. I now know how to deal with these feelings, and what I need to do to make myself feel better (i.e. sleep, Netflix, phonecall with Mum, chocolate). I will most likely always have depressive tendencies, because depression is naturally my coping mechanism when things get tough, but I know that I'm not back to square one when I do feel down, and I still feel proud of myself for how far I've come.
4) It will probably make you a better person
With the perspective of coming out the other side of a mental illness, I now feel like I have a lot to thank my depression for. I definitely think that it will make me a better doctor, because I'm able to relate to those with mental illnesses and I know what I would want someone to tell me if I was in that situation. I also understand how difficult recovery is and the reason that patients keep relapsing - I think I can be quite patient in that way. And in general life, I find that I never judge anyone because you don't know what is going on in their own head, behind closed doors. If someone is nasty to me, I brush it off because who knows what they are dealing with?
5) Never feel ashamed to get the support you need
I think this is the most important point in this post. Never feel ashamed about your mental health, and never let stigma stop you from getting the help you need. Whether it's medical help, counselling, asking for support from friends or family, or taking some time off work - do it. Your health is one of the most important things you have, and mental illnesses are just as valid and debilitating as physical illnesses. Your job will allow you to take time off, and may even offer you some extra support. Health professionals are out there to help you, and will never feel like you are wasting their time. And your family and friends will just want you to feel better, and would hate to realise that they could have helped you but you didn't ask them for any help. Asking for help is the first step towards recovery.
The difference between who you are and who you want to be is what you do.