It is not confidence when you think you can do it later, it is laziness and arrogance.
Why not do it now while you still have a lot of time? why not do it now while the pressure is lesser and you can still think clearer? You have more power now, you have a lot of momentum now so why not do it now?
Maybe you are really tired but you can pause. You are allowed to slow down but never allow yourself to rest for a long time. Never think that you will be stronger later and things will go smooth because it never will. Something bad will always happen in the worst possible time. Unexpected events can occur. Brownout can happen, rain can happen, additional task may be assigned to you etc.
If you decided to do it later, you will become lazy even more. Sometimes your mind will even tell you to do it tomorrow which is a very bad thing. If you think can do it later, you are hallucinating that you have a lot of time. You think you are fast but when the execution time is there... you can't even move your feet. Simply because you are already feeling the high pressure and worries are starting to take over.
So do it now even if you feel so tired, do it now even if you think you can't continue.
You will find the energy once you continue, your momentum will start to go strong. Just keep moving forward because you will feel better in a while.