This time of year we may see new teachers looking haggard and feeling stressed and depressed. They might be saying, "Is this worth it?" and "This is so much harder than I thought!" If you are a mentor to a new teacher experiencing this phase of disillusionment, there are some things you can do to help your new teacher through this phase.
Emotional
Emotionally we can support new teachers by providing encouragement and listening. We can give positive feedback and help them keep perspective. Continuing to develop that trusting relationship and lifting their spirits can be one of the most powerful things you can do as a mentor. Find out their favorite treat (chocolate works wonders) and bring them an encouraging note.
Instructional
Teachers going through disillusionment may benefit from positive feedback on things you see them succeeding at. They may 
need help/support with lesson planning. Sitting with them to reflect on their teaching highlighting positive things they have done may boost them back up. This may also be a good time to model lessons for them or video one another to observe teaching in both classrooms. Support them in planning and scheduling testing as they move forward.
Logistical
Parent-teacher conferences can cause some anxiety and stress for new teachers. Help them with planing for conferences and offer advice as needed. You can help with finding resources to help them and getting supplies ready for them. They may need a reminder of grading policies and help with copies. Be observant and you might see ways you can alleviate some extra stress from their life.
For more information on teacher phases, check out this article.