Will a servant be rewarded for acts of worship that he finds burdensome, despite being sincere in them, and what does this feeling of burden indicate?

The reward for striving in obedience is great with Allah, so persist in it until you reach a level where worship becomes your aspiration and you perform it with a joyful heart. For the pleasure and intimacy in obedience come only after enduring the pain of striving and subduing the self. A lover finds delight in serving and obeying their beloved, and the more the love increases, the greater the pleasure of obedience. Some of the Salaf (pious predecessors) described their happiness in prayer and standing (in devotion), and the Prophet, peace and blessings be upon him, likened it to the coolness of the eyes. This pleasure and delight cannot be attained except through initial patience and toil. After that, the soul transforms from compulsion to cheerfulness and contentment, and sluggishness and relapse disappear, so that the bliss of the seeker lies in their journey and diligence, and their torment in their sluggishness.