The best advice I can give people suffering from mental health issues is to keep your mind in the present moment. Most worry is about things that happened in the past that can't be changed or in the future that hasn't even happened yet. Instead of listening to the internal voice in the head, be aware of all your senses and you will realise that your mind( that causes unpleasant feelings) is only a small part of your reality. The key to this is mindfulness, to catch your mind wandering and be present with your conscious mind instead of the sub-conscious running the show. When you are conscious, you can reprogram the damaging effects of the sub-conscious with positive programming.
I have a more extreme way than most with dealing with life's suffering: that has been a strong dedication to meditation, sometimes practicing over 10 hours per day living in monasteries but I realise this life is certainly not for most people and I don't want to preach religion on here but I would like to list some secular books that I believe can help people with mental health issues, these are:
The power of now- Eckhart Tolle
Take off your glasses and see- Jacob Liberman (a book about eyesight but equally insightful about improving your life)
The Open Focus Brain- Les Femhi.
I am more than happy to answer any questions if anyone wants to PM me.
One last thing, keep your head up(literally), this will make you feel better.We are the only species on Earth that has an upright spine but we choose to slouch. Just look at how Melbourne players perform when they have their heads down.
Stay strong and be happy.