Don't know that anyone is born to it, maybe those who have had easy lives can. For those who have been through a fair fit, it can be a struggle. There are days when I feel down and remind myself that the joy of the Lord is our strength - think its part of fighting the good fight. Rejoice in all things, at all times - regardless. Pretty soon the blackness dissipates and I feel better, part of spiritual warfare for those with certain calling. I renounce the dreaded Ds: depression, despondency etc. Takes a bit of effort but it works and gets easier as your faith grows. Plenty of reference in the Psalms about praising in spite of difficult circumstances :)