Generally, if you have created copyright material which you own, you will not need to get permission to copy. However, care needs to be taken in making assumptions as to who owns certain rights in copyright material, because there may be restrictions on its use. For example, if you created certain material in the course of employment as a lecturer or in accordance with a research contract, your employer or funder may own the copyright or may have imposed conditions on its use.
For teachers, it cannot be assumed that material owned by the Ministry of Education can be used without restriction (although often content may be available under an open access licence). If you have published your own material, any transfer or licence you have granted to a publisher may have an impact on what you can do with the material.