Here is something wich drives me crazy: assuming you have a 2-way time machine(fully functional), and you're going to the past, where in that specific time in the past the past-you were there(presuming you've never seen anything that had to do with a time traveler before), then how is it possible, presuming the time traveler-you DO meet the past-you?
The problem is: if you haven't seen in the past the future-you realtive to the past, then if you go to the past and meet you past-self, then it is likely you create ANOTHER reality in wich you enter as soon as you get there(unless you have the ability to be phased-out of the universe, i.e you affect 100% nothing) in the past, and you can never return to YOUR timeline.
That might be the answer, another reality.
Think of THIS: you're in a time traveling Car, in a race(a Drag race or a realitivly straight sprint race with no traffic in an urban terrain).
after a minute or so you plan on tricking the other racers by being at your EXACT position 10 seconds earlier.
PRESUMING that it is impossible to create or enter another timeline, can you do the time travel presuming you HAVEN'T seen a copy of your car and you inside it?