Enduring difficulty for a meaningful purpose is a sublime pleasure.
Any person who is seriously desirous of achieving real happiness (Krishna Consciousness) must seek out a bona fide spiritual master and take shelter of him by initiation.
Spirit and matter are completely contradictory things. All of us are spiritual entities. We cannot have perfect happiness, which is our birthright, however much we may meddle with the affairs of mundane things. Perfect happiness can be ours only when we are restored to our natural state of spiritual existence.
As the materialists are thinking that happiness is all in sense gratification, they don't see the happiness in serving Krishna, that's where the real happiness is achieved in much higher relationship and higher purpose. Their thought is, "Alright Dharma, ardha, kama, moksha" now we will make money, enjoy our sense gratification and at the end of life go for moksha. Howvere in devotional service, we know about prema, the prema is actually the love for Krishna. It is the highest perfection and Krishna is the highest happiness also.
Our happiness, our joy is simply to know that we are doing the will of Guru and Krishna, that's all. We don't need anything else.
Ungrateful heart means miserable frustrated life and grateful heart is always happy.