There is so much in this world that shouldn't exist.
There are so many lives that shouldn't unfold the way they do.
There are so many difficult situations.
There is so much pain.
There is so much hunger.
There is so much compromise.
There is so much and so many that are limited and undernourished.
There is so much sickness.
There is so much inaction.
There is so much denial.
There is so much ignorance.
There is so much judgement and discrimination.
There is so much dishonesty.
There is so much wrong with the world. Sometimes it seems like there is no place to start fixing it all, because each problem invades the others and nothing is ever simple enough to just fix.
All of this is true - but the experience of being overwhelmed can hinder you more than the sheer scope of the task at hand. This doesn't mean that you shouldn't acknowledge the magnitude of the problems we face - but that magnitude should not cause you to spiral downward in an experience of pessimism and 'it's too much'. Any task can be accomplished by taking it one step at a time.
Allowing yourself to feel overwhelmed causes you to stop looking at the situation clearly and rationally and leads you to to be more easily influenced by your emotional turmoil, which will cause you to be ineffective in what you're doing. Think about someone you know who is always blowing things out of proportion - they do not see clearly what is around them, they are influenced by their state of mind. When you start exaggerating and speaking or thinking dramatically then you know that you're not looking at what's in front of you with clarity - your vision is clouded by hazy lenses of emotional energy, spurring you on to think more irrationally and imagine even more irrational scenarios.
Yes, there is so much in this world that would cause you to cry in despair at its existence for eternity - the reality is that if you allow yourself to do this then you are not contributing to the solution to the problems, you are just another symptom.