Why do chess coaches encourage their students to play stronger players? I am a 1400 rated player. We have 4 players in our club rated 2000+. If I sat down and played 100 games against one of them, I would lose 100 games. So, how does losing 100 games against one of these strong players EVER make me a better player? [sadly, none of them ever gives a post mortem].
It's partially who the opponent is, and partially how much better the opponent is.

I've gone from ~1750 to almost 1900 in the last year (approximate as ECF grades - 142-158 to those who understand ECF). In that time I've played a lot of players who are appreciably better than me. But not massively better; most have been 1850-2100. That meant I could still give them a challenge, even if I was stretched to hold them for the whole game. In fact a major moment in that improvement was I when I had to play my first ~2050+ player in that period, I was sort of doing OK but a little worse, and then I suddenly realised he a had let me off the hook. This 2050 player had made a mistake! I can not explain quite how much confidence that gave me, and I went on to draw the game, and in fact missed a win along the way. The whole episode set me up for the season, and the game is below.

So that's the first point, good enough so that you see and understand their plans, and that they stretch you, but also not so good that it's wham, bang, thank you mam. The second point is that a lot of the players I have played in this period have been kind enough to go through the games with me. This helped me understand their expectations, and often showed me ideas that I had not even considered. This was coupled with has the 2100+ player at my (small) club helping me, The later in particular clarified my impressions of my opponents plans, helped me identify some of my tactical weaknesses and showed me what both of us had missed over the board.

So for you I suspect 2000+ is a bit rich. But look for players who are


Around 100-300 higher than you 
Are kind enough to spend at least a few minutes afterwards going through the games 
And then take the games to your trainer to check your opponent wasn't talking rubbish


Anyway here's the game that I referred to earlier. It's at move 19 I had my epiphany.

[Event "A Match in the League"]
[White "Ian Bush"]
[Black "Somebody Scary"]
[Result "1/2-1/2"]
[WhiteElo "148"]
[BlackElo "178"]
[FEN ""]

1.e4 c5 2.d4 cxd4 3.c3 dxc3 4.Nxc3 e6 5.Nf3 Bc5 6.Bc4 Nc6 7.O-O a6 8.Qe2 
    ( 8.e5 )
8...b5 9.Bb3 Nge7 10.e5 Ng6 11.Ne4 Be7 12.Nd6+ Bxd6 13.exd6 O-O 14.Bg5 f6 
15.Bd2 Nge5 16.Rac1 Bb7 17.Nxe5 fxe5 18.f4?! 
    ( 18.Bc2 )
18...exf4 19.Bxf4 Qh4 
    ( 19...Nd4! )
20.g3 Qh3 
    ( 20...Nd4! )
21.Rfd1 Qf5 22.Bc2 Qf6 23.Qh5 g6 24.Qc5 Rab8?! 
    ( 24...Rac8! )
25.Bb3 Rfc8 26.Qe3 Rf8 27.Rc5 Rbc8 28.h4 Na5 29.Rxc8 Rxc8 30.Bxe6+ dxe6 
31.d7 Rf8 32.d8=Q 
    ( 32.Bg5! Nc4 33.Bxf6 Nxe3 34.d8=Q Rxd8 35.Rxd8+ )
32...Rxd8 33.Rxd8+ Qxd8 34.Qxe6+ Kg7 35.Be5+ Kh6 36.Bf4+ Kg7 1/2-1/2