If you find it hard being "in a good mood" then step back and do a drop set. A drop set is a weightlifting term. When the current weight is too tough, lower the weight a little bit and get some more reps in. How can this look spiritually? You first of all NEED to be reading scripture every day but if you find it hard to understand or you don't see the point of the book you are in. Take a step back, start the book over again or start a book or two back to get the right context. 

Another way you may feel life is too heavy is you are filling your head with conflicting things. I heard the old saying "If you have two dogs, one good and one bad. Which one will win in a fight? Whichever you feed most." If you are feeding your flesh more than your spirit then it's no wonder you are in a bad mood. When I eat garbage and don't rest I won't have a good workout and drop sets won't really help because I am sabotaging myself. FEED YOUR SPIRIT, GET REPS IN, PUT LOVE OUT