Is it unwise to raise PHP's memory limit?

A website I’m currently working on is quite heavy which resulted in a memory allocation error. Now, this can be solved by raising the “memory_limit” in PHP’s settings so enough memory is available, but is this a wise thing to do? I don’t really have many ideas on how to improve the performance of my scripts so I don’t know what else to do, but raising the limit doesn’t sound very wise to me.