Is it obligatory to supplicate for one's needs in every prayer, and does interrupting the supplication then returning to it have an effect?

It is not obligatory to repeat a specific supplication for a particular need in every prayer, but it is recommended. Persistence in supplication and repeating it at all times, especially during prostration (sujud), is among the reasons for its acceptance, as prostration is the closest a servant can be to his Lord. The predecessors described the best supplication as one characterized by persistence and humble entreaty to Allah. Supplication is an act of worship, and whoever does not ask Allah incurs His wrath.