Confidence is extremely important in the thesis writing process. Indeed, if you plan on finishing your thesis on time (or at all), it is very important to learn to trust your own judgment…
There are times when mentors (e.g. PhD supervisors, your thesis chair, members of your thesis committee) may make suggestions that don’t make sense to you. For example, a mentor might suggest that you collect additional data — which you know is not necessary — and furthermore, will put you considerably behind schedule in your thesis writing. Another example… you strongly believe that your research calls for a qualitative approach, however, one of your mentors is suggesting that you use quantitative methods. Moreover, there may be occasions when one member of your thesis committee is advising you to do something that contradicts the recommendations of another member of your thesis committee. In this situation, whatever you do, you are not going to be able to please everyone!
If you give careful consideration to your mentor’s suggestions and they simply are not helpful, then have the confidence to defend your position. Whether the issue relates to your methodology, your conceptual framework, or something else, have the courage of your convictions, and clearly explain your position (in writing if necessary). If you allow yourself to be easily swayed in a direction that is not in keeping with your vision of the project, the danger is that you will get confused and disillusioned — and you literally could end up… not finishing your thesis. As such, you absolutely must have the confidence to show your committee members that you know what you are doing.
Ultimately, remember that this is your project; you are the expert in this area. Unless your mentors did the same thesis as you — which obviously won’t be the case — you should know more than your supervisors about the topic. Therefore, it absolutely makes sense to politely defend your decision.
Final thought: you’ll need to be able to defend your thesis at your PhD defense, so it’s not a bad idea to get in some practice early on in your thesis writing journey!