Are the deeds one forces oneself to do and covenants with Allah to perform less rewarded than those done voluntarily?

The reward for obedience depends on its validity and acceptance. The one who performs an act of worship with a good heart and a cheerful disposition deserves the full reward. Some scholars have mentioned that whoever performs an act of worship with cheerfulness and ease is better than one for whom it is burdensome, because he has surpassed the stage of struggle. However, if an act of worship is difficult for the soul, it is necessary to strive against oneself to perform it if it is obligatory, and one is not required to make a vow or a pledge to motivate oneself for it.