Mr Self Destruct

Watching Breaking Bad recently (It's a show I've gotten into lately along with Game of Thrones), I was wondering about me and if my depressive tendencies will lead me towards a path of ultimate self destruction. It wasn't a bad day today but it wasn't the best. 
And when you have another in a long line of not the best day(s) you tend to get tired of them, weary of them. Tired and weary of battling yourself and your mind and when that happens the question of suicide sometimes pops up. 
How much longer can I keep battling this? 
Battling this part of me, illness though it is, takes its toll. I mean, will it come to pass that one day in the far future will I just reach a point where I've had enough and decide to end it? That's a scary thought. One in a very long line of scary thoughts granted but scary it still is. Things are ok at the moment but when they aren't this thought occasionally appears. 
Will I survive? Do I have it in me to keep surviving?