Learning to cope with the frustration of your plans & wishes is a very important lesson in flying.
If you learn it well at this stage (ie accept it happens & not let it affect your judgement or get you down) then in the times to come once you have your licence (and it does happen eventually), your decision making will be much improved.
At the moment your instructor is able to make an objective & experienced call on whether or not conditions are right for you - this will not always be the case.
Down the line, when you have planned your flight, assembled your passengers, got everyone to the airfield and then find that you feel a little "uneasy" about the conditions (which I find a good indicator that I'm in denial about conditions / forecasts being marginal for my own specific capabilities) then you should be able to make the "Not Go" decision far more easily and with far greater objectivity.
The alternative, as many of us will attest to, is (at best) a much shortened flight and / or a flight worrying about landing conditions that you wish you had not committed to
.
Keep at it - it was a long haul with extreme highs & lows for many of us on here.
Regards, enq.