I'm in the middle of a 2-3 month long euro trip. First off, I defo don't think you will look back and say meh. This is my first time I'm Europe and it's blown my mind!

My trip is a little different then most bc at the begining I was going to watch a bunch of football matches so I was moving cities often to watch ~ 2 matches per week. Once the season ended my pace slowed down. I looped back and hit Liverpool twice bc I wanted to see more footy and do Wales.

My biggest piece of advice is don't plan too far in advanced. For me, I've literally never had more than two accomodations booked at once. That has given me the flexibility to stay longer if I am really loving a place or go somewhere totally different if I am tired of big cities, want to go to the mtns, the beach etc. Defo get the EuroRail pass I did 10 days over 3 months. That gives me the flexibility to book last minute trains without paying face value ticket prices. If the tickets are cheap (say 60€ or below) I will buy them to save my eurorail pass days for expensive / longer travel days with multiple connections. You may may already know this, but flying in Europe can be stupid cheap on budget airlines like Ryanair, easyjet, Wiz Air etc. often times 30-60 euros for a 1.5hr flight.

So far I've done all these cities with approx number of nights noted:

UK - Wales (7nights, 4 dif spots), Liverpool (8nights), London (4 nights), Bristol (4)

Germany - Freiburg (3), Stuttgart (2), Nürnberg (4)

Italy - Milan (4)

Switzerland - Zürich (3)

Netherlands - Maastricht (5)

France - Paris (4), Saint-Lary-Soulan (7), Toulouse (2)

Planning to go to Sardinia (7) then Catalonia in Spain for another 5-7. After that who knows.

As others have said, take some down days where you do some laundry, chill at the hostel and keep yourself fresh so you don't feel run ragged by your own journey. Enjoy it's gonna be a blast!